Abstract
In Taiwan, rice husks are plentiful agricultural waste. The rice husks are treated primarily as waste. Some rice husks are used such as organic manure, fodder, etc. From the energy point of view, rice-husks can be used as biomass fuel. In the recent years, tests were carried out to study the feasibility of recovering the heat energy from rice husk combustion. In this work the operating parameter effects on rice-husk combustion were investigated in a pilot scale vortexing fluidized bed combustor (VFBC).
The experiments were carried in a pilot scale VFBC, a 0.64m×0.32m rectangular combustion chamber constructed of freeboard with 0.45m inside diameter and 4.85m in height. The first-air flow rate, secondary-air flow rate, and bed temperature and the primary-air ratio (the ratio of primary air flow rate to the total air flow rate) were investigated.
The results of this study indicated that the combustion proportion in the bed increased with the primary air flow rate, but decreased with the bed temperature. The secondary-air flow rate had no effect on the combustion proportion in the bed. The combustion proportion above the secondary-air injection was largely influenced by the combustion proportion. In the in-bed oxygen rich condition, the combustion efficiency increased with the secondary-air flow rate, but decreased with primary-air flow rate and bed temperature. Therefore, lower temperature (600°C) combustion with a lower primary-air flow rate is recommended.
