Improvement of combustion efficiency and minimizing CO and NO emissions of a swirling fluidized-bed combustor firing rice husk

In this study, a swirling fluidized-bed combustor (SFBC) using an annular spiral air distributor was fired with rice husk. In order to control NO emission from the combustor, rice husk was moisturized by adding water to ldquoas-receivedrdquo fuel, while CO emission was mitigated via injection of secondary air into the bed splash zone. The SFBC was tested at constant fuel feed rate for variable fuel-moisture content and primary air supply. Effects of the fuel quality and excess air on radial and axial temperature and gas (O₂, CO and NO) concentration profiles in the reactor, as well as on the combustion efficiency and emissions, are discussed. Effective control of CO and NO emissions and high (> 99%) combustion efficiency are achievable when firing moisturized rice husk in this SFBC.