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1Indian Cement Industry Strives Towards Environmental ExcellenceKamyotra J.S; Bala S.S.; Gupta P.K. & Tiwari Ankur
Central Pollution Control Boardand
Nath K R P; Bohra A; Selvarajan M; Tiwary N K; Pahuja A & Mishra A KNational Council for Cement and Building Materials
ABSTRACT:An industry can not successfully run in an economic, social and environmental vacuum.Indian Cement Industry strives for continual improvement in achieving environmentalexcellence through technological upgradation, energy and resource conservation.Especially over last two decades, the importance of environmental impact has been wellrecognized by cement plants. The installed capacity of Indian cement industry has grownten fold in last three decades with an average growth rate of 8% and in last three years theproduction rate has increased to around 9%. However, the per capita consumption ofcement in India is around 200 kgs only, which is much less than the world average of 500kgs. The installed capacity and production of Indian cement industry during 2012 are 330and 240 Mn.T respectively. The production of blended cements (Portland Pozzolonacement and Portland Slag cement) in the year 2011-12 was as high as 67% as against 36%in 2000-01 of total cement production. Indian cement industry started using variousindustrial, municipal and agro wastes as alternate fuels in order to conserve the naturalresources of conventional fuels. With such environmental improvement initiatives thetotal average CO2 emission from cement industry was reduced to 0.72 tCO2 / t cementfrom substantially high level of 1.12 tCO2 / t cement in 1996. Indian Cement industry hasbeen proactive for the preservation of ecological balance inspite of damage caused due tomining of limestone by developing green belts, harvesting of rain water, recharging theground water etc. This paper discuses some of the important environmental issues ofIndian cement industry viz., gradual improvement in control of different emissions likeparticulate mater, Oxides of nitrogen, sulphure dioxide which has helped statutory bodyfor revising/evolving standards for the emissions. Prevailing technologies world over arealso discussed for control of the emissions in cement industry.Key words: Cement Industry, Particulate Matter, Pollution Load, Gaseous Emissions,Oxides of Nitrogen, Sulphur Dioxide, Control Technologies, Air Pollution ControlEquipments1. INTRODUCTIONAll over the world the cement industry is striving for improving energy efficiency,product quality, and environment. The world cement production is 3.6 Bn.T during theyear 2012 among which China is leading by producing 2137 Mn.T and Indian cementindustry stood second with production of 240 Mn.T. There are 183 major cement plantsand 365 mini cement plants in India.Indian cement industry has largely set up or retrofitted energy efficient plants orprocessing equipment for various sections for better productivity. Plant puts its bestefforts for cost reduction and quality improvement of its product through differentmeasures to maintain and improve its position in a highly competitive market. Taking full
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2advantage of the technological developments that have taken place over the past two andhalf decades, the Indian cement industry transformed itself into a modern, energy efficientand environmental friendly industry.The past achievements and the on going efforts of the Indian cement industry giveconfidence that it will soon attain the best bench marks in world in all aspects ofproductivity and sustainable development.2. ENVIRONMENTAL ASPECTS OF THE CEMENT INDUSTRYEnvironmental aspects of the cement industry in this paper cover air & water. Air qualityis one of the major parameter. Air quality reflects ambient air quality, fugitive dustgeneration and point source emissions. The emissions from cement industry to theenvironment viz., dust, carbon dioxide, Carbon monoxide, Oxides of Nitrogen, Oxides ofsulphur etc are discussed below. Cement industry contributes around 5% of the globalCO2 emissions. Cement manufacturing process does not use water, but operations likemill cooling and gas conditioning towers consume water.
2.1. AirIn India around 98% of the cement is produced by dry process technology, only around2% is produced by wet & semi dry process. Cement industry consists of variouscomminution operations viz., crushing & grinding of raw materials & coal and finishgrinding cement. During these size reduction operations at various sections dustemissions are generated. During pyroprocessing various gaseous emissions are generated.Indian cement industry, Central Pollution Control Board and State Pollution ControlBoard have played pivotal role in reducing emissions from this sector.
2.1.1. Ambient Air QualityUnder the provisions of the Air (Prevention & Control of Pollution) Act, 1981, the CPCBhas notified fourth version of National Ambient Air Quality Standards (NAAQS) in 2009.This revised national standard aims to provide uniform air quality for all, irrespective ofland use pattern, across the country. Various pollutants monitored under Ambient AirQuality, their limits, and methods of measurement, etc as per NAAQS are given below inTable-1.
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3Table-1: National Ambient Air Quality Standards (NAAQS)
2.1.2. Fugitive Dust EmissionsCentral Pollution Control Board hadpublished a report on Assessment offugitive emissions & development ofenvironmental guidelines for control offugitive emissions in cementmanufacturing industries in the year2007 covering information on varioustypes of fugitive dust emission sources,control measures and regulations indeveloped countries and evolvedguidelines for prevention and control offugitive dust from cement plants. Thisenabled cement plants to adopt variousmeasures to control fugitive dustemissions on sustainable basis. Fig-1: report on Assessment of fugitiveemissions & development of environmental
guidelines for control of fugitive emissions incement manufacturing industries
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42.1.3. Point Source EmissionsMajor point sources for particulate matter emissions are viz., crusher, coal mill, raw mill,kiln, cooler, cement mill sections. Central Pollution Control Board has taken initiative fordevelopment of emission limits for NOx and SO2, development of load based emissionnorms for particulate matter (PM) and also revision of present concentration basedemission norms for PM from kiln stacks of cement plants of Indian cement industry.National Council for Cement and Building materials (NCB) and Central Pollution ControlBoard (CPCB) studied jointly in this regard to formulate emission standard for Indiancement plants.3. INITIATIVES TOWARDS ENVIRONMENTAL EXCELLENCE
3.1. NCB Study for Development of Emissions NormsNCB collected the plant data through data format covering plant age, technology andpollution control measures etc. After assessing the secondary data provided by variouscement plants, CPCB and NCB selected 14 major cement plants and 3 mini cement plantsconsidering the age, technology, geographical location, raw material and fuel consumedfor the detailed study by monitoring of PM, NOx and SO2 and other parameters. In thestudy emissions from major point sources of cement plant like Crusher, Coal mill, Rawmill & kiln, Cooler, and Cement mill for Particulate Matter (PM) were monitored.
3.1.1. Particulate Matter EmissionsIt has been observed that concentration of PM emission is not so significant like earlierdays. The technology to control dust emissions has been upgraded in a wide range in lastthree decades. Various Air Pollution Control Devices (APCD) viz., Bag filters, ESP andHybrid filters are being used by the industry. Most of the cement plants had replaced ESPwith Bag houses to control emissions from Kiln & Raw mill stack. Reverse Air BagHouses, bag house with glass fiber membrane filters has high efficiency in controlling theemissions from kiln & raw mill stack. To know the status of technology adaptation byvarious cement plants, they have been categorized according to their age as plantscommissioned before the year 1990 as old plants, commissioned during the years 1990 to2000 as modern plants and plants commissioned after the year 2000 as new plants.It has been observed that majority of the dust emissions are from kiln & raw mill stackthat accounts for about 55-65% of the total dust emissions from the major point sourcesof cement industry. The statistical analysis of emissions from kiln & raw mill stack aregiven below in Fig-2. With installation of bag house with poly tetra fluoro ethylene(PTFE) glass fiber membrane filters which has an efficiency of 99.99% filtration with theminimum emission of 16 mg/Nm3. whereas with conventional filters the highest emissionof 95 mg/Nm3 was also observed. The average emission from kiln & raw mill stack ofvarious cement plants was 42 mg/Nm3.
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5Statistcal Analysis of PM Emissions from Kiln & Raw millStack
42
95
1625
0102030405060708090
100
Average Maximum Minimum St Dev
PM Co
ncentr
ation, m
g/Nm3
Average Maximum Minimum St Dev
Fig-2: Statistical Analysis of PM emissions from Kiln & Raw mill StackThe frequency distribution graph is given in Fig-3, which gives there are ten plants out of14 major cement plants monitored having the emission in the range of 0-50 mg/Nm3 andonly 4 cement plants having emissions in the range of 50-100 mg/Nm3 and none of theplants have the emissions above 100 mg/Nm3.
Frequency Distribution of PM Emissions fromKiln & Raw mill stack (mg/Nm3)
10
4
02468101214
0-50 50-100
No. o
f Plan
ts
0-50 50-100
Fig-3: Frequency Distribution of PM Emissions from Kiln & Raw mill stackAs discussed above on age categorization, emissions from various ages of plants wereanalysed. The statistical analysis of PM emissions on the basis of plant age is given inFig-4. The new cement plants have the emission maximum of 34 mg/Nm3 and minimumof 16 mg/Nm3 whereas the modern plants have a maximum emission of 76 mg/Nm3 andminimum of 19 mg/Nm3. In the old plants the emissions was little high compared to thenew and modern plants with a maximum of 95 mg/Nm3 and minimum of 38 mg/Nm3.
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6Statistics of PM Emissions based on Plant Age
34
76
95
16 19
38
0
20
40
60
80
100
New Modern OldAge Category of Cement Plants
PM Em
ission
in mg
/Nm3
PM MAX PM MIN
Fig-4: Statistical Analysis of the PM Emissions on Age of the plant Basis3.1.2. Oxides of Sulphur (SO2):
In dry process cement plants due to inherent heat exchange among material and gases theSO2 emission is very nominal. The sources for Oxides of Sulphur are raw material andfuel which consists of sulphur in the form of elemental or as sulphur compounds. Thesesulphur compounds gets absorbed in the various zones of the kiln. But the sulphurcompounds which can not be absorbed are emitted along with the exit gas.Control for SO2 emissions in pyroprocessing can be exercised by one of the threemethods: inherent removal by the process, process alterations, and by using SO2scrubbing technologies. In-line raw mill is efficient process of inherent removal that canbe accomplished by passing the kiln exhaust gases through raw mill for drying of rawmaterials while grinding. Many cement plants have incorporated this method for reducingtheir SO2 emission levels. Other methods for reduction or control of SO2 emissions areinjection of dry reagents like adding quicklime or hydrated lime into the riser duct andwet SO2 scrubbing etc.The sulphur dioxide (SO2) emissions varies from BDL to 1700 mg/Nm3, the highestemission was observed at a wet plant and plants using limestone having pyretic sulfur.The Statistical analysis of SO2 emissions from 44 cement kilns monitored by NCB aregiven below in Fig-5.
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7Satistical Analysis of SO2 Emissions (mg/Nm3)
118
1707
0
341
020040060080010001200140016001800
Avg Max Min Std Dev
SO2 E
mission
s in m
g/Nm3
Avg Max Min Std Dev
BDL
Fig-5: Statistical Analysis of the SO2 EmissionsThe frequency distribution of SO2 emissions from kiln & raw mill stack is given below inFig-6 which describes around 22 cement kilns having the SO2 emissions within thedetectable limit and around 18 cement plants having emission in the range of 10-100mg/Nm3. only four plants having the emission above 100 of which one plant is usingnorth eastern coal and three plants are using limestone having high pyretic sulphur.
Frequency Distribution of SO2 Emissions (mg/Nm3)
22
18
4
0
5
10
15
20
25
100
No of
Plan
ts
100
Fig-6: Frequency distribution of the SO2 Emissions3.1.3. Oxides of Nitrogen (NOx)
The NOx emission is one of the major gaseous pollutants from kiln stack. NOx isgenerated from four mechanisms viz., Thermal, Fuel, Feed & Prompt NOx. NOxemissions comprise of 90% or more of the nitric oxide (NO) and remaining 10% arenitrogen dioxide (NO2) and other oxides of nitrogen that are emitted from cement kilnstack. NOx is generated during pyroprocessing and it is influenced by the operational
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8conditions like flame temperature, turbulence & momentum, Nitrogen content in the fueland kiln feed, percentage of oxygen, excess air in the pyroprocessing system.NOX emissions are controlled in cement industry by different techniques & practices.
i. Process modificationsii. Combustion modificationiii. NOX removal control
Process modifications are usually done to reduce heat consumption, to improve clinkerquality, and to increase the lifetime of the equipment (such as refractory lining) bystabilizing process parameters. Process modification improves fuel efficiency, reduceoperating costs, increase capacity & kiln operational stability. Since NOX formation isdirectly related to the amount of energy consumed in cement making, improving fuelefficiency & productivity reduce NOX emissions. Continuous monitoring of oxygen &carbon monoxide emission in the cement kiln exhaust gases indicates the amount ofexcess air. At given excess air level, NOX emission increases as the burning zonetemperature increases. Maintaining the burning zone temperature at the minimumnecessary values of excess air would minimize both the process energy requirement & theNOX emissions.Combustion Modifications like installation of Low NOx burners and Low NOx calcinerare also helpful in reducing the NOx emissions up to 20-30%. Low NOX burner systemswhich rely on the staged combustion of feed and fuel.It has been observed that a NOx emission varies from 184 to 1237 mg/Nm3 at 10% O2,depending on type and capacity of plant technology, raw material and fuel. Plant datawere analysed in the present study for NOx emission for 25 Kilns have reported values inthe range of 265 to 2675 mg/Nm3.
Statistical Analysis of Oxides of Nitrogen (mg/Nm3)
587
1237
184 221
0200400600800100012001400
Avg Max Min Std DevNOx
Emiss
ion Co
ncen
tratio
n inmg
/Nm3
Avg Max Min Std Dev
Fig-7: Statistical Analysis of the SO2 EmissionsThe frequency distribution of NOx is given in Fig-8, it gives that the maximum number ofemissions observed in the range of 500-800 mg/Nm3 at 19 plants and next to that at 15cement plants in the range of 200-500 mg/Nm3. there are 7 cement plants having
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9emissions in the range of 800-1000 mg/Nm3 and only one plant above 1000 and 2 plantsbelow 200 mg/Nm3 are observed.
Frequency Distribution of NOx
2
15
19
7
102468101214161820
1000NOx Concentration in mg/Nm3
No of
Plants
1000
Fig-8: Frequency distribution of the NOx Emissions3.1.4. Pollution Load of Particulate Matter
Dust emission per tonne of clinker has been calculated for various sections of cementplants monitored. The pollution load varied in the range of 0.001 to 0.007 kg/ tonne ofclinker for crusher, from 0.02 to 0.277 kg/ tonne of clinker for kiln & raw mill, from0.015 to 0.085 kg/ tonne of clinker for cooler, from 0.005 to 0.057 kg/ tonne of clinker forcoal mill, from 0.002 to 0.045 kg/ tonne of clinker for cement mill. The total pollutionload including the all major stack varied in the range of 0.056 to 0.345 kg/ tonne ofclinker depending on performance of APCD and process technology adopted. It has beenobserved that the raw mill & kiln section accounts for about 54 % of the total pollutionload of all major stacks of the cement plant. The distribution of pollution load fromvarious sections is given below in Fig-9.
DISTRIBUTION OF EMISSIONS FROM VARIOUS POINTSOURCES OF CEMENT PLANTS
1%
54%
11%
25%
9%
Crusher Kiln/RM Coal Mill Cooler Cement Mill
Fig-9: Distribution of Emissions from Various Point Sources of Cement Plants
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The statistical analysis of the pollution load of Kiln & Raw mill stack gives the maximumpollution load of 0.28 kg/tonne of clinker and minimum of 0.02 kg/tonne of clinker. Theaverage pollution load from kiln & raw mill stack was 0.1 kg/tonne of clinker. Thestatistical analysis of pollution load from kiln & raw mill stack is given below in Fig-10.Frequency distribution of dust pollution load from kiln & raw mill stack gives, around 9plants are having load less than 0.125 kg/tonne of clinker and 4 plants are having load inthe range of 0.125-0.25 and only one plant has the load above 0.25 kg/tonne of clinker.The frequency distribution graph of PM pollution load of kiln & raw mill stack is givenbelow in Fig-11.
Pollution Load from Kiln & Raw Mill Stack
0.28
0.02
0.100.07
0.000.050.100.150.200.250.30
MAXIMUM MINIMUM AVERAGE SDPoll
ution
Load
in kg
/tonn
e of C
linker
MAXIMUM MINIMUM AVERAGE SD
Fig-10: Statistical Analysis of the Pollution Load of Kiln & Raw mill stack
Frequency distribution of Pollution Loadfrom Kiln & Raw Mill Stack
9
4
10123456789
10
0-0.125 >0.125-0.25 >0.25-0.375Pollution Load in Kg/Tonne of Clinker
No of
Plan
ts
0-0.125 >0.125-0.25 >0.25-0.375
Fig-11: Frequency distribution of Pollution Load from Kiln & Raw mill stackPollution load was calculated for individual plants with respect to the actual flow rate andactual rate of production at different dust concentrations load of 50, 75, 100 and at 150mg/Nm3. Statistical analysis of pollution load of cement plants was done and it gives thatthe maximum pollution load from kiln & raw mill stack are 0.28, 0.27, 0.41, 0.55 and0.82 Kg/Tonne of Clinker at the dust concentration of at actual value measured, 50, 75,
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100, and at 150 mg/Nm3 respectively. The statistical analysis of estimated value ofpollution load of kiln & raw mill section are given below in Fig-12.
Measured and Anticipated Pollutin Load from Kiln & Raw mill Section
0.27
0.41
0.55
0.82
0.020.06 0.10
0.130.19
0.10 0.130.20
0.26
0.39
0.28
0.000.100.200.300.400.500.600.700.800.90
Pollution Load atMonitored
emission value
Pollution Load at50 mg/Nm3
Pollution Load at75 mg/Nm3
Pollution Load at100 mg/Nm3
Pollution Load at150 mg/Nm3
kg/To
nne o
f Clin
ker
MAXIMUM MINIMUM AVERAGE
Fig-12: Statistical Analysis of Estimated Pollution Load of Kiln & Raw mill section3.1.5. Resource Depletion and Sustainable Development
Sustainable development objectives can be met through large use of non conventionalfuels including waste derived fuels, manufacture of blended and composite cements,improving energy efficiency through retrofits and adoption of energy efficient equipment,co-generation of power through waste heat recovery system etc. With its excellent trackrecord in the adoption of state-of-the-art technologies and the best manufacturingpractices, its constant endeavors in energy conservation and environmental improvementand its new initiatives in the utilization of WDF and co-generation of power throughwaste heat recovery, the Indian cement industry has been able to serve the cause ofsustainable development over the years and in fact has brought down the CO2 emissionlevel from 1.05 tonne of CO2 / tonne of cement in 1994 to 0.72 tonne of CO2 / tonne ofcement in 2010.
3.2 Water Consumption & waste water generationCement-making process is not water-intensive. The water consumption for themanufacturing of cement is low for dry process but high for wet and semi dry processes.Moreover, many plants are located in areas where water is scarce. The amount of water acement plant consumes depends on the technology it adopts. The dry process of cementrequires a limited quantity of water for mill cooling, GCT etc. If a cement plant isequipped with a captive power plant, then the requirement for water-increase substantially.Water is also used for dust suppression and Green Belt Development / plantation purpose.For this purpose the cement plants draws water from different sources like bore wells-ground water (27%), surface water -rivers (39%) and harvested water - mines pit & others(33%) are fulfilling the necessities of the plant.
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As most Indian cement plants are located in remote areas, their staff colonies also usewater. Typical water consumption pattern of a cement plant shows that Waterconsumption by plant for cooling & others accounts 50% water used, captive powerplants 23%, for plantation 2-3 % and staff colonies & domestic purposes uses 25% ofwater consumed. The water consumption in dry process plants varies from 0.12 to 1.4 Kl/tonne of cement depending up on the plant capacity and age of the plant and staff colonyconsumption and green belt development. On an average 0.5 Kl of water is consumed forproduction of one tonne of cement. In wet process plants it went up to 2.8 Kl/tonne ofCement.Waster water generated from staff colonies are collected and treated in sewage treatmentplants using various sewage treatment techniques like activated sludge process, tricklingfilters, UASBR (Up flow Anaerobic Sludge Blanket Reactor) and root treatment plants.After treatment disinfection processes like ozone treatment, UV treatment andchlorination is done before reusing it for green belt development, dust suppression and incooling purposes etc. Statistical analysis of water consumption by Indian cement industryis given below in Fig-13.
Statistics of Water Consumption in Indian Cement Industry
0.12
2.8
0.51
00.51
1.52
2.53
Minimum Maximum Averagem3 o
f Wate
r/ton
ne of C
ement
Minimum Maximum Average
Fig-13: Statistical Analysis of Water Consumption by Indian Cement Industry4. CONCLUSIONWith the development of various technologies & compulsions to compliance withregulations framed by statutory bodies for the benefit of the industry as well ascommunity, control of emission levels not only of dust but other gaseous pollutants NOxand SO2 has gained momentum over the years. Norms of various stack emission levels forpollutants have been enacted or proposed in various countries for cement industries. Withabove NCB study, CPCB has proposed emission norms for the gases viz., NOx & SO2,Load based emission limits for Particulate matter from Kiln & Raw mill section andrevised standard for the concentration based emission limit for particulate matter. Cementindustry is working on improving the quality of environment by adopting varioustechnologies and due norms will further help them in achieving a green cement industry.ACKNOWLEDGMENTThis article is being published with the permission of Director General, NCB.
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Bibliography:1. Comprehensive Industry Document on Cement Plants, Central Pollution Control
Board (unpublished developed by NCB)2. Life Cycle Assessment on Cement Industry, Ministry of Environment and Forests,
New Delhi3. Assessment of fugitive emissions & development of environmental guidelines for
control of fugitive emissions in cement manufacturing industries, 2007, CentralPollution Control Board
4. National Ambient Air Quality Standards, Nov 2009, Ministry of Environment &Forests, New Delhi
5. Guidelines for the Measurement of Ambient Air Pollutants, May 2011, CentralPollution Control Board
6. Formation and Techniques for Control of Sulfur Dioxide and Other SulfurCompounds in Portland Cement Kiln Systems, Portland Cement Association 2001
7. Activity Report 2012, Cembureau, The European Cement Association8. Cement Statistics 2011, Cement Manufacturers Association, India9. Annual Report 2011, Ambuja Cement Ltd10. Annual Report 2011, ACC Ltd11. Low Carbon Technology Road Map for the Indian Cement Industry, 2013
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