Pollution

India didn’t need to let power producers emit more of deadly oxides of nitrogen; here’s why

Limiting NOx emission at 300 mg / Nm3 is doable, claims Finnish state-owned Fortum Oyj; Environment ministry relaxed norms to 450 mg / Nm3 in October

 
By Soundaram Ramanathan
Published: Tuesday 08 December 2020
Achieving the 300 mg / Nm3 limit of emission of lethal oxides of nitrogen from coal-fired thermal power plants was possible by installing the state-of-the-art primary solutions, according to Fortum. Photo: Surya Sen

The Union Ministry of Environment, Forest and Climate Change (MoEF&CC) recently let power producers emit more of lethal oxides of nitrogen (NOx); but a Finnish state-owned company has now claimed sticking to earlier, stricter, relatively climate-friendly norms is not as tough as it was made it out to be.

Fortum demonstrated recently that NOx emissions could be capped at 300 milligram / normal cubic metre (mg / Nm3 ) on all loads in India inside coal-fired power stations.      

The Centre, on October 19, 2020 increased the limits to 450 mg / Nm3 from 300 mg / Nm3 for plants commissioned between 2003 and 2015 after the power sector lobbied hard and argued meeting the norms would be tough. 

According to Fortum, however, emissions can be kept within 300 mg / Nm3 by any or all of the following solutions:

  • Staged combustion - Supply only a part of the air required by stoichiometry in the burner area and the remaining 20-40 per cent via the over fire air (OFA) system. It is used in most applications.
  • Use of low-NOx burners - With new or modified burners, some additional advantages (besides NOx reduction) can be achieved. These include flame stability, fast ignition, good flame shape and wide turn-down ratio.
Elevated levels of NOx affect respiratory tracts and make those with respiratory infections and asthma more vulnerable. This can lead to chronic lung diseases. Such gases can reduce the lungs’ defence against bacteria, making them more susceptible to infections. Also, sunlight triggers photochemical reaction in such gases that can cause the formation of ground-level ozone and secondary particulate matter formation.

 

NOx-reduction measures are tailored depending on the boiler dimensions, auxiliary equipment, fuel quality and other conditions at the power plant. Reducing them can also improve efficiency of coal plants, the company said.

Implementing these solutions on site, however, can take up to one year.

According to Vikas Mehta, chief manager, business development, Fortum India Pvt Ltd:Achieving less than 300 mg / Nm3 should not be an issue. People generally have this misconception that just changing some components in the furnace will help reduce NOx. Alteration or replacement of boiler burner may lead to 10-15 per cent reduction in NOx emissions. More changes have to be done in terms of air flow, fuel flow staging to reduce NOx near burners.”

The company said it was willing to provide technical support to effectively operate the system. The lowest level of emissions that could possibly be achieved using state-of-the-art primary NOx reduction technology is 200 mg / Nm3.

Further reduction must be done by adopting flue-gas treatment technologies such as selective non-catalytic reactors (SNCR) or selective catalytic reactors (SCR), according to experts present at the conference. 

SNCR and SCR are more expensive than primary state-of-the-art technologies.

European coal-based power plants have been meeting stricter NOx limits than Indian coal-based power stations. While existing coal-based thermal power units in Europe have limits to emit no more than 165mg / Nm3 , those in India are allowed to emit up to 450.

Maggie Wiatros-Motyka, analyst, International Energy Agency, Clean Coal Centre, also supported the use of sych technology.

About the experience of designing low-NOx solutions in India, the company advised stakeholders to check the reliability of instruments which measure pollutant data at the site for correctness.

According to New Delhi-based think tank Centre for Science and Environment, this raises questions on the reliability of data from continuous emission monitoring systems. Such equipment in chimneys are used to measure and send data on pollutants such as particulate matter, sulphur dioxide, oxides of nitrogen, etc in the flue-gas ’round the clock.

The data, however, remains unutilised for regulatory compliance, hence making monitoring complicated.

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