Numerical study on oxy-co-firing of pulverized coal and rice straw in a 300kW research furnace

This work aims to reveal the characteristics of pulverized coal and straw oxy-co-firing in a 300 kW vertical research furnace through reacting flow simulations. Effects of coal/straw blending ratio are systematically assessed. A 3-D model of the swirl burner and the furnace is first constructed for the simulations. Composition of oxidizer is 30% O₂ and 70% CO₂ and the excess oxygen is fixed to 15% in this study. It is found that the distance required for devolatilization and the low temperature region in the central region are extended with greater particle size and higher blending ratio. To maintain the thermal loading while increasing the blending ratio, the overall fuel feeding rate is increased since the heating value of straw is half of coal. The increase of fuel momentum also alters the recirculation flows. NO and SO₂ emissions are influenced by the composition of fuel blends, i.e. blending ratio. The NO concentration increases and SO₂ decreases with more straw in the fuel.