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Combustion modification to reduce NOx emissions also improves energy efficiency

Jyrki Holappa  ·  07 September 2020

Amidst the process of replacing fossil fuels with renewable energy sources it is of vital importance to improve the energy efficiency and reduce the environmental damages caused by thermal power production. Implementing advanced combustion technology not only significantly reduces the generation of harmful NOx emissions, it simultaneously enhances the plant performance through the optimisation of boiler operations.

Chimney of a CHP plant against clear blue sky.

The role of conventional energy producers is changing. While thermal power plants still produce more than half of India’s electricity, the increasing share of renewable energy available on the energy market and the tightening limits on maximum allowed nitrogen oxides (NOx) emission levels in power production are constantly prompting energy producers to make decisions on investing in expensive emission control equipment whilst trying to maintain productivity and operational efficiency. The task is challenging for several reasons – and not least due to uncertainties in the timelines.

For the power producers, profitable business in the current situation requires the capability and knowhow to run the power plants more flexibly than before, yet coal-fired power plants have been designed to operate full load. The designed performance regarding minimum load and load ramping speed for coal-fired power plants are typically not met in actual operation. Furthermore, most coal plants have also not had strict requirements on start-up time or start-up time reliability.

This is why the bulk of power plants face challenges when required to operate reliably and efficiently at lower loads. The consequence is increased coal consumption versus produced electricity and the adverse impact of an unplanned trip of the plant. What is more, resulting from low and fluctuating production volumes and increased strain for the facilities, the pressure to reduce fuel costs increases – and that, in turn, creates the need to procure a wider range of fuel types.

Coal costs typically represent as much as 80% of the total operating expenses. Assuming that coal cost would be 50 USD/ton, reducing the coal costs by 5% corresponds to an annual cost savings of approximately 4MUSD and the annual reduction in coal consumption is more than 75 thousand tons of coal.

Fortum, a power utility and asset owner, started already back in the early 1990s to develop a solution for its own fleet to cut down NOx emissions without compromising energy efficiency. We learned that combustion modification implemented to a sufficient extent not only reduces NOx emissions but also enables more flexible operation and, consequently, energy efficient and cost effective utilisation of coal plants, making it possible to adapt to the changes in the energy system and maintain profitability.

The solution developed by Fortum is based on implementing advanced NOx reduction technology at the stage of boiler combustion, which is the primary source of emissions. The combustion is stabilised by modifying or exchanging the entire burner taking into account the amount of air required. By stabilising and improving the combustion it is possible to operate burners at lower loads without risk of losing the flame. In addition, based on our experience, due to the more stable combustion and tuning of the combustion, we are able to increase the efficiency by 0.5–1.0%.

Fortum has since supplied more than 1200 Low-NOx burners in more than 50 projects globally. Regarding corner- or wall-fired pulverised coal-fired power plants in India, we have proved that Fortum’s solution is feasible and can be implemented at any local power plant in India, including those using domestic coal. In 2020, Fortum completed a combustion modification on one of the coal-fired power plants with a capacity of over 100 MWe. The NOx emissions were for the first time cut down to such extent that NOx levels reached well below 300 mg/Nm3 in all loads and mill combinations.

NOx emissions of a coal-fired boiler daily averige below 300mg/Nm3.

This reference project has demonstrated that Fortum’s solution works well in Indian boilers with a wide range of coals, both domestic and imported. In addition to this, Fortum has carried out technical feasibility studies on tens of different boiler types in India. These studies are based on documents and information received from local power plants as well as on actual site measurements conducted by our experts using special instruments. Even the 15-20-year-old power plants have potential to improve their energy efficiency and reduce their air emissions significantly, as in the case of NOx emissions, by adopting the best available technologies, where meeting these requirements with optimal CAPEX and OPEX is crucial.

The task is extremely challenging because of the energy sector’s importance to economic growth and because of the scale of coal-fired power production in India. More than 77% of the country’s total electricity generation is based on coal firing (250 GW) and 73% of that capacity (150 GW)* has been built after 2004, meaning that these power plants have more than half of their designed lifetime left. The coal used in Indian thermal coal-fired power plants is substantially domestic coal. The pressure to deal with job and business loss in and around the power plants will be immense.

As a service provider, Fortum has gained comprehensive experience in designing and implementing low-NOx combustion refurbishments of thermal power plants, and it has undertaken combustion system modifications as an independent contractor for boilers originally supplied by different original equipment manufacturers (OEMs) for tangential, wall- and top-fired boilers.

We are happy to serve you. Our combustion expertise and technology can increase your plant’s profitability without compromising on environmental commitments.

*) Coal-Based Power Norms: Where do we stand today. Centre for Science and Environment, New Delhi. 2020.

Jyrki Holappa

Jyrki Holappa

General Manager, Business Development, Asia
Tel: +358 50 453 2705
jyrki [dot] holappa [at] fortum [dot] com

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