Combustion behaviour of pulverised coal in high temperature air condition for utility boilers

• Novel burner can realise both conventional and HTAC mode without any unstable.
• HTAC can be established with a combustion air temperature as low as 185 °C.
• Substantial NOx reduction can be achieved under HTAC mode.

High Temperature Air Combustion technique (HTAC) is expected to improve the combustion efficiency and NOx emissions of fossil fuels. This paper presents the results from experimental measurements under steady combustion mode conditions and during the change from conventional air combustion mode to HTAC mode of a newly proposed burner configuration. A 1.2 MWth pulverised coal fired furnace has been used to evaluate the characteristics of HTAC and conventional combustion. To realise both the HTAC and the conventional modes, is one of the important HTAC technological tasks for practical use in utility boilers. During the start-up process, HTAC operation mode cannot be achieved because the air for combustion is still cold. Therefore burner configurations for both modes, conventional and HTAC, are required. In this study, a new burner is proposed and the start-up procedure of pulverised coal fired boilers adopting HTAC is demonstrated. The newly proposed HTAC burner enables successful operation mode switching in both ways between conventional and HTAC modes.The study shows that HTAC can achieve NOx reduction whilst maintaining sufficiently high combustion efficiency. The flat and high in-furnace temperature suggests a possibility of being able to use a smaller boiler furnace.