| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 96 === The study adopted interconnecting the riser (0.0529 m i.d. × 3 m height) and the bubbling fluidized bed (0.28 m i.d. × 0.55 m height) and researched the cold modeling of chemical looping combustion (CLC) for Geldard group B powder (glass beads, dp = 230 μm). The riser acted as air reactor and the bubbling fluidized bed as fuel reactor. The solids circulating rate was measured by tracking solids and was controlled by a loop seal valve. The superficial gas velocity of the riser and solids circulating rate were the variables to investigate the pressure profile, pressure fluctuations, pressure drop, standard deviation of pressure and axial voidage distribution measured by the pressure taps and observed the hydrodynamic and stability of the system. Simulated the solid conversion against reaction time at different temperature, pressure and diameter referring to solid oxygen carrier’s parameter and calculated the production of carbon dioxide.
It was found that the choking on the experiment was classified as B-type choking induced by blower or standpipe. The riser operated from turbulent fluidized bed to fast fluidized bed. The pressure profile showed that loop seal was the highest pressure of the system. As for CLC, the sealing effect of the loop seal was able to avoid diluting carbon dioxide with nitrogen and leakage of carbon dioxide form fuel reactor into the air reactor. Therefore loop seal is the core of CLC.
For the bed material (glass beads), the average axial voidage distribution in the riser changed with superficial gas velocity and solids circulating rate. It appeared a straight line on dilute phase conveying and a simple exponential or S-shape profile on fast fluidization.
On the gas-solid reaction for unreacted shrinking core model of unchanging size, the gas film diffusion control on the NiO/YSZ and NiO/bentonite can both be neglected. According to the solid conversion of NiO/bentonite against reaction time figure, the reaction rate increased with the rising of temperature and pressure and the reduction of solid oxygen carrying’s diameter. The productivity of dioxide carbon showed that NiO/YSZ (Ishida et al., 1996) is more suitable than NiO/bentonite (Ryu et al., 2001) as solid oxygen carrier in the chemical looping combustion system due to the high reactivity of NiO/YSZ.
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