Experimental study on rice husk combustion in a circulating fluidized bed

Circulating fluidized bed combustion has proven to be an effective way of converting biomass wastes into clean energy. This paper introduces the experiment study on rice husk combustion in a circulating fluidized bed. Experiments on a cold model show that rice husk is difficult to be fluidized, and adding silicon sand and coal improves the fluidization condition. Effects of sand diameter, gas velocity and mass fraction on rice husk mixing were tested. The rice husk can mix well with 0.3–0.8 mm sand at gas velocity 0.8–2 m/s. Experiments on 1 MW thermal test facility show that rice husk ignition temperature is only 340 °C, much lower than coal. The gas velocity and air split have great effect on rice husk combustion. At proper operation condition, the rice husk combustion efficiency reaches 97%, and the carbon content in fly ash is between 3% and 8%, whereas CO emissions varies from 200 to 800 ppm, SO2 ranges from 50 to 100 ppm and NOx ranges from 150 to 220 ppm.