Assessment of the Impact of Under-Fire Air Introduction on the Pulverised Coal Combustion Efficiency

The objective of the present work was to analyse the effect of the air redistribution on the flow field, temperature profiles and combustion efficiency, in a pulverised coal-fired utility boiler. The change is due to an under-fire air (UFA) introduction through ports located at the bottom of the furnace. Computational fluid dynamics (CFD) modelling technique is used for investigation of the aerodynamic behaviour of the gas-solids mixture, combustion efficiency, temperature profiles and concentrations of gaseous combustion products in a furnace of an utility boiler of 225 MWe power plant unit. The modelling results are compared with a test matrix of measurements at different boiler operating conditions. The comparison between the numerically obtained and measured temperature profiles, as well as energy loss due to inefficient combustion, shows satisfactory compliance. The analysis of the results concerning the near-burner regions indicates the occurrence of intensified swirl and improved combustion efficiency, as under-fire air flow rate was increased.

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