Combustion of Peanut Shell in a Vortexing Fluidized Bed Combustor with Flue Gas Recirculation

• Main Authors: Yuan-Jie Wang, 王源杰
• Other Authors: Chien-Song Chyang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/26426894465545238676

碩士 === 中原大學 === 化學工程研究所 === 101 === Peanut shell is common agricultural waste in Taiwan, and its high calorific value is suitable to be used as biomass fuel for fluidized bed combustion. In this study, the experiments are conducted in a vortexing fluidized bed combustor (VFBC) using silica sand as bed materials. The combustor has a height of 4.6 m. The combustion chamber is 0.8 m × 0.4 m in area and freeboard has an ID of 0.75 m. The secondary gas is introduced into the freeboard tangentially at 2.05 m above the air distributor plate. Different operating conditions, including excess oxygen ratio, stoichiometric oxygen ratio in the bed, and particle sizes, are used to investigate their effects on the axial temperature profile, pollutant emissions, combustion efficiency, and combustion fractions. Furthermore, in order to understand the vortexing effect, with a fixed total oxygen rate of 0.8175 Nm3/min and primary gas rate of 3 Nm3/min in the furnace, nitrogen is added to secondary gas in 4 separate runs with the rate of (0, 0.44, 0.75 and 1 Nm3/min), respectively. The results showed that crushed peanut shell can cause bridging in the hopper during the feeding process; therefore, compressed shell pellets is the best way to solve the feeding problem. As excess oxygen ratio increases, both of crushed and pelletized peanut shell have higher bed temperature and combustion efficiency. As stoichiometric oxygen ratio increases, different results for crushed and pelletized peanut shell are observed. This is due to the different major combustion locations from different particle densities of the two fuels. Axial CO and NOx profiles indicate there are two specific regions inside the reactor, i.e. formation and decomposition. The CO emission from the vortexing FBC is found to be in the range of 55-73 ppm for crushed peanut shell and of 45-60 ppm for pelletized peanut shell, with excess oxygen ratio of 40-60%. In every experiment, combustion efficiency of peanut shell is always over 99%.