Ministry of Environment, Forest and Climate Change (MoEF&CC) brought a Notification vide General Statutory Rules (G.S.R.) 96(E) on 29th January 2018 - for industrial boilers. Unlike the previous ones, this notification specifies standards and limits based on fuel used in the boiler. Earlier, the standards and emission limits were based on the steam generation capacity of a boiler. The norms specified are as follows:
The boiler used in the industries, namely (1) sugar (2) cotton textiles (3) composite woollen mills (4) synthetic rubber (5) pulp and paper (6) distilleries (7) leather industries (8) calcium carbide (9) carbon black (10) natural rubber (11) asbestos (12) caustic soda (13) small boilers (14) aluminium plants (15) tannery (16) inorganic chemical and other such industries using boilers, shall adhere to emission norms in the said notification from the date of its applicability that is 29th January 2018.
Although for the boilers using Agro-based fuel and Natural Gas as fuel, there is no standard specified for sulphur dioxide and oxides of nitrogen, it is required to meet stack height criteria notified vide G.S.R. 176(E), dated the 2nd April 1996. In no case, the stack height shall be less than 11 metres. However, for the small boilers using coal or liquid fuels, the required stack height with the boiler shall be calculated by using the formula
Total stack height in metres from ground level (H) = 14 Q^(0.3)
Q = Sulphur dioxide (SO2) emission rate in kg/hr. This can be calculated from a stack monitoring report by multiplying concentration of SO2 in mg/Nm3 with the Rate of Emission given in Nm3/Hour and further converting milligram (mg) to kilogram (kg).
For example, in case of a boiler with SO2 emission of 40 mg/Nm3 at a rate of 2000 Nm3/Hour; Q will be calculated as 0.08 Kg.
Now, the important note is that GSR 176(E) stipulates emission limits for small boilers under Schedule I at serial No. 70 of Environment (Protection) Rules, 1986. These limits superseded the earlier limits notified under Schedule I at Sr. No. (34) vide GSR 742 E, dated 30 August 1990. But GSR 96(E) does not mention anywhere that it has suppressed the previous notifications not it has superseded. Therefore, it could be interpreted that the emission standards specified in this notification are in addition to the prevailing norms, where Particulate Matters remains a crucial standard parameter. Boilers were categorized into 4 types based on steam generation capacity. The emission limit deliberates on the followings parameters:
Please note that the test results given here in the above table are representative and not actual. Further, the test report may also contain data of Carbon Dioxide (CO2), Oxygen (O2) and Moisture Content, besides, exhaust gas temperature, velocity, and rate of emission. It may also be noted that the Emission Regulations (Part-III) published by the Central Pollution Control Board (CPCB), MoEF&CC and also Standard Method IS 11255 series published by the Bureau of Indian Standards has specified standard formats of reporting of stack monitoring results.