Coal-to-gas conversion |


Burners prior to dispatch (Photo: RJM International)


also ensured that legacy brownfield systems were modernised, including upgrading the Rothemühle air heaters.


Designing a new coal-to-gas burner Reconfiguring a coal-fired power station to convert it to fire natural gas is not a simple procedure, if the plant is to operate at its original design capacity, reliably, flexibly and cost-effectively. This is particularly the case for older plants where the challenge is to gather sufficient data and measurements and to gain enough understanding of the plant’s limits, in order to devise an appropriate solution. This means that no RJM project is ever the same – one size does not fit all. The calorific value, thermal dynamics and combustion attributes of gas are very different to those of coal. Designing new burners that can achieve a combination of ultra-low emissions and a flame profile that will not damage the integrity of the burner mouth or the boiler walls can only be achieved by a detailed programme of CFD modelling that considers every variable, such as fuel properties, fuel and air flow distribution,


and combustion performance, and how these variables impact on MWe output and emissions. The conversion retained the existing BFG burners, maintaining this prudent utilisation of a calorific waste product gas from the nearby steelworks that would otherwise have to be flared off. This was a key requirement of the Aboño 2 coal-to-gas conversion project.


Also, with power plants preparing the next stage of their transition to low-to-zero carbon power generation, RJM’s new burners had to be designed to fire up to 10% hydrogen as a secondary fuel. Hydrogen releases no emissions upon combustion and so its use delivers an immediate NOx


and CO2


reduction. RJM’s new coal-to-gas burners were also designed to have the potential to fire a greater percentage of hydrogen as a further step towards lower carbon generation at a later date.


Major performance improvements Following the Aboño 2 coal-to-gas conversion, all the key emissions metrics were significantly reduced and other performance improvements recorded:


First fire, with one row in service (Photo: RJM International)


New burner being installed (Photo: RJM International)


1.3 million tonnes per annum of coal no longer being fired; primary NOx


reduced by 70% to 250 mg/Nm3 CO2


emissions of 130 mg/Nm3


emissions of 845 mg/Nm3 ;


emissions reduced by 870 000 tonnes per annum, a reduction of 30%; SOx


Additional environmental benefits from using BFG as a second fuel, reducing emissions of CO2


by a further one million tonnes per annum;


5 MWe of parasitic load freed up, delivering an improvement in cycle efficiency of about 0.4% (coal yard, flue gas desulphurisation plant, conveyors, hoppers, mills and classifiers no longer needed);


improved flexibility, reliability and availability; plant life extension; and improved environment for the local community (noise, smell, views, etc). This ground-breaking project was completed on time, within budget and met all the exacting performance upgrades asked of it. It also demonstrates that coal-to-gas conversions can play a meaningful role for generators as they embark on their transition to zero carbon generation.


RJM is currently carrying out a similar coal-to-gas conversion for a plant operated by Omaha Public Power Department in Nebraska, United States.


“This has been a successful project,” commented Diego Martinez, Commissioning Engineer at Wood plc, “meeting all our performance guarantees.”


Further information:


https://www.durofelguera.com/en/edp-and- corporacion-masaveu-award-duro-felguera-the- Aboño-gas-conversion-project/


https://www.woodplc.com/solutions/case-studies/  through-fuel-switching


https://www.rjm-international.com 40 | November/December 2025| www.modernpowersystems.com reduced to zero;


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