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About FAQ Stack Height
The stack heights of the Sterlite copper is designed as per the consent conditions and emission standards stipulated by TNPCB. Further, whenever the plant expanded its facilities, from 391 TPD to 900 TPD to 1200 TPD, it has followed the then prevailing CPCB stipulations.
The EPA Notification [S.O. 64(E), dated 18.01.1988] does not mention stack height details for sulphuric acid plants. The stack height shall be one prescribed by the Respondent Pollution Board based on Section 21 (5) (iv) of the Air Act. Accordingly, stack was built at 60.38 metres as per consent order and subsequent yearly consents obtained basis the same.
It is specific to mention that all previous consents granted by TNPCB specifically imposes a condition with respect to stack height at 60.38 mts. after scientific assessment of the emission load and metrological conditions before grant and renewal of such consents and address any apprehension of public and safeguards the public interest.
The reasons for a 165m stack height for the expansion project (Plant-II) are:
- In Plant-II, the acid plant facilities have a single stack and hence the height considered is more than the stack height of the existing plant.
- Being a new project and in order to have least impact on the existing overall ground level concentration (GLC), the mathematical modelling basis for stack height of 165 metres of the Copper Smelter Expansion Plant-II, ensures an incremental SO2 ground level concentration* (in ambient air) of just 12.44 µg/m3 over the baseline of 30.9 µg/m3 bringing overall ground level concentration to 43.34 µg/m3. This is significantly lesser than the NAAQ (National Ambient Air Quality) Standards of 80 µg/m3
The SO2 emissions from Sterlite Copper are very insignificant due to emission control equipment and utilization of SO2 gas for manufacturing the sulphuric acid unlike any power plants, which vent the entire SO2 gas through stack without any utilization or scrubbing. In view of the high SO2 emission levels in the power plants, MoEF has notified emission norms and mechanisms to curb emission vide notification no. S.O. 3305 (E) dated 07.12.2015.
The SO2 emissions from Sterlite Copper contributes to only 1-2% of total SO2 emissions of Tuticorin. The NAAMP ambient air quality data monitored by TNPCB for the past 20 years reveals that the Sulphur Dioxide and NOx emissions in the aforesaid three monitoring stations are within the norms.