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Point source and ambient air quality emission standards
Air emissions are the major pollutant generated from cement plants. Standards/limits for both point source and ambient air quality enacted by pollution control boards are discussed below.
Point source emissions
The point source emissions from the cement industry include dust/particulate matter and gaseous emissions. Since the cement industry deals with various size reduction operations from limestone crushing to clinker grinding, dust emissions are a major pollutant. Gaseous emissions such as sulfur dioxide (SO2), oxides of nitrogen (NOX), carbon monoxide (CO), carbon dioxide (CO2), etc., are generated during pyroprocessing.
Particulate matter (PM)
The major sources for particulate matter emissions are crusher, coal mill, raw mill, kiln, clinker cooler, cement mill and packing plant. Cement plants are equipped with air pollution control equipments (APCEs) like electrostatic precipitators (ESP), baghouse with glass fibre membrane filters and ESPs modified with bag filters, called hybrid filters.
MoEF has notified the dust emission standards for cement plants in 1986, which was subsequently revised with gazette notification no.G.S.R.46 (E), dated 3 February 2006. The emission standards for cement plants and grinding units are given below:
- For plants with a production capacity of 200 tpd or less the total dust emissions (all sections) should not exceed 400 mg/Nm3.
- For plants with a production capacity greater than 200 tpd the total dust emissions (all sections) should not exceed 250 mg/Nm3. However, the Central and State Pollution Control Boards may fix harsher standards, not exceeding 250 mg/Nm3 for smaller plants and 150 mg/Nm3 for larger plants, if the industry is located in an area that, in their opinion, requires more stringent standards.
- For existing plants (plants commissioned before 03-02-2006), including grinding units, located in critically polluted (as per the guidelines of the CPCB) or urban areas with a population of one lakh and above (including 5 km distance outside urban boundary) the emission limit is 100 mg/Nm3.
- For new plants, including grinding units (plants commissioned on or after 03-02-2006), the emission limit is 50 mg/Nm3.
Gaseous emissions from kiln stack – NOX and SO2
Emissions of NOX from cement plants are mainly due to excess primary air, fuel and burning process at higher temperature during clinkerisation. In Indian cement plants, there are no significant SO2 emissions from clinkerisation but it may be generated when the limestone has a high sulfur content. Coal from northeast India may also have a high sulfur content.
CPCB is in the process of evolving emission norms for the Indian cement industry. CPCB and NCB had carried out a study to develop emission norms for the cement industry. However, some of the state pollution control boards have set up emission limits for NOX and SO2 emissions from the cement industry.
Mercury and heavy metal emissions
Emissions of mercury and other heavy metal emissions are required to be monitored during co-processing of hazardous waste by cement plants and reported to the respective SPCB and CPCB.
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This article is abridged from the original, which was included as ‘Keynote: Environmental Regulations in India’ in the October 2013 issue. The issue is available for subscribers to download by signing in here.
Read the article online at: https://www.worldcement.com/asia-pacific-rim/09102013/environmental_regulations_in_indian_cement_industry4_276/