Mathematical modelling and optimisation of lignite and wheat straw co-combustion in 350 MWe boiler furnace

•In-house developed code upgraded with biomass particle reactions during co-firing.•Selected sub-models of coal and biomass devolatilization modified and applied.•Optimal conditions predicted for 10% thermal share and 500 µm particles of biomass.•Shape of biomass particles affected fuel trajectories and flame significantly.•Proper fuel distribution decreased losses due to unburnt C in fly and bottom ash.