EXPERIMENTAL STUDY ON FUEL COMBUSTION FROM RICE STRAW IN AN ATMOSPHERIC BUBBLING FLUIDIZED BED COMBUSTOR

Abstract

Vietnam is an agricultural country with abundant biomass potential. Over 55 million tons of biomass is generated yearly in Vietnam but only 30-40% is used for energy production, most of which is distributed to households for cooking. The agricultural waste (rice straw pellets-RSP) is a suitable fuel for the fluidized bed combustors. An experimental combustion study using the RSP as fuel was performed in a 75 to 90 kW_th (kW- kilowatt) atmospheric bubbling fluidized bed combustor. The effect of different variables such as sand diameter, temperature, fluidization velocity and mass fraction on rice straw pellet mixing on the combustion efficiency and flue gas emissions were investigated. Experimental results have shown that the RSP can mix well with 0.1…1.25 mm sand at gas velocity approx. 1.2…1.5 m/s, the optimal RSP combustion temperature is within the range from 750 to 800° C. The concentration of flues gas such as carbon monoxide (CO), nitrogen dioxide (NO₂/NO_x) and sulfur dioxide (SO₂) was compared to German emission limit (TA-Luft 2002). As the results concentration of NO_x in flue gas was a bit higher whereas that of CO and SO₂ was lower.