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We were discussing “Cements and its types” and “Clinker grinding process in cement manufacturing unit” in our previous posts. We have also seen the “Clinker storage system” in our recent post. 

Today we are going to start here one very important topic i.e. Cement industry pollution control measures. 

We will understand the various terminologies and engineering concepts used in cement technology with the help of this category, but first read this article “Clinker cooling technology” and “Cement kiln refractory lining”.

Further we will go for discussion of clinker grinding, cement packing and dispatch, pollution control and much more facts about cement technology in our next post in this category of cement technology.

Sources of pollution and control technology

Water pollution

Cement industry is not a water polluting industry. Only the cooling tower blowdown associated with the GCT is a source of waste water generation, which does not have much significance as a water pollutant. The waste water is treated in septic tanks or sewage treatment plants and is used for gardening, irrigation and other purposes.

Air pollution

Cement industry is one of the major air polluting industries. The source of dust emission may be categorized into following parts 

Point Emission Source: - from raw mill, kiln, clinker cooler, cement mill, coal mill.
Fugitive Emission Source: - The dust generated from the transfer of raw materials,   intermediates and final products and during loading / unloading.
Kiln is the main source of dust emission.

Quantum of dust generated and recommended air pollution control equipment

5 - 15
Bag Filter
Raw mill :
 Gravity discharge
 Air swept

20 - 80
300 - 500

Bag Filter / ESP
Coal Mill :
 Gravity discharge
 Drying / grinding

20 - 80
100 - 120

Bag Filter / ESP
Kiln : Dry
 Semi - dry
50 - 75
10 - 20
30 - 50

Bag Filter / ESP
Clinker Cooler
 5 - 10
 ESP / Bag Filter with H.E
 Cement Mill
 60 - 150
Bag Filter / ESP
Packing Plant
20 - 40
Bag Filter

The dust emission can be controlled by providing adequate pollution control equipment such as cyclone, ESP, bag - filters etc. Their selection depends upon various factors, such as mentioned here
1.      Size of dust particles
2.      Flue gas characteristics
3.      Collection efficiency
4.      Emission limits prescribed by authorities
5.      Techno - economic feasibility

Gaseous pollutants from the kiln are oxides of N (NOx) and SO2. Ammonia is injected into the flue gas in the high temperature zone at exit of the kiln where NOx is reduced to N2 in the presence of O2.

NO + 4 NH3 + O2 = 4 N2 + 6 H2O
NO2 + 4NH3 + O2 = 3 N2 + 6 H2O

Hydrated lime Ca (OH) 2 is injected into the flue gas to arrest SO2.
Ca (OH) 2 + SO2 + ½ O2 = CaSO4 + H2O

Plant Capacity
Emission Standards for Particulate Emission ( mg / N m 3 )

 200 tpd or less
 Greater than 200 tpd
 Protected area Other areas
 250 400
 150 250

Noise Pollution

Noise is generated from operation of heavy duty machines - crushers, tube mills, ball mills, fans, coolers etc. Noise level depends upon nature, size and capacity of machines, running speed, feed material etc. The noise level generally varies from 70 - 118 dB.

Following methods may be employed to control noise pollution in cement industry
1.      Using vibration damping pads, isolating vibrating parts etc. to reduce noise pollution in cement industry
2.      By enclosing the source and making them sound insulated
3.      Using personal noise protectors like, ear plugs, ear muffs etc

De-dusting and Pollution Control

Various types of pollution control equipment are intensively used in the cement industry to minimise dust nuisance in the plant area so as to maintain dust free atmosphere as far as practicable as well as to maintain the dust emission level within acceptable limits.

Cement plant machinery work under negative pressure to prevent dust from escaping into the atmosphere.

The different types of dust are  

1.      Raw material and Raw mix dust
2.      Coal dust
3.      Exit dust from raw material dryers
4.      Exit dust from kilns
5.      Clinker dust
6.      Raw gypsum dust
7.      Cement dust

The Pollution - control equipment used are

1.      Electrostatic precipitator ( ESP )
2.      Dust - bag Filter
3.      Gravel - bed Filter
4.      Glass bag - house.

Do you have any suggestions? Please write in comment box.

I am very thankful to Mr. Subrata Bhaumik, Independent cement consultant, for providing such beautiful information and contents about cement technology. 

Mr. Subrata Bhaumik has more than 50 (Fifty) Years (1965 - 2016) of Experience in Cement and other related Industry covering more than 100 assignments in cement plants with capacities ranging from 100 tpd to 10,000 tpd in India and abroad involving visit to 25 countries overseas in connection with work.

For more detailed information about the original Author of this content, please click the Author profile link below.

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