| Summary: | 碩士 === 立德管理學院 === 資源環境研究所 === 94 === In this study, the anaerobic fluidized-bed reactor (AFBR) was fed with acetic acid and nutrients. As the reactor reached steady state (two different organic loadings were conducted), recirculation rate was varied to obtain different liquid superficial velocity (ul) and the dynamic bed-expansion experiment (DBEE) was conducted. The effect of internal biogas on gas holdup �n�v�捥), pressure drop (�嵐), and expanded-bed height (Hb) was explored. Followed by stop feeding influent till without biogas production in the AFBR, the DBEE was conducted again. Finally, the DBEE was conducted with external gas injection. And thus, different hydrodynamic characteristics among internal metabolic biogas, without biogas, and external gas injection were clarified.
At steady state, as the volumetric loading rate was increased from 3.83 to 7.65 g COD/L-d, the biogas production rate (Qg) was doubly increased. Biofilm thickness (��) of the lower part of the AFBR was smaller than that of the upper part, whereas the particle density (�漥) of the lower part was larger than that of the upper part. This means that a phenomenon of stratification exists in the AFBR.
Results of DBEE (ul = 0.61 ~ 1.53 cm/s) showed that the gas hold-up at the case of internal metabolic biogas production (�捥,IBP) was less than that at the case of external gas injection (�捥,EGI), regardless of the lower biogas production rate (Qg) (0.66 L/hr for test run 1) or the higher Qg (1.30 L/hr for test run 2). However, the two (�捥,IBP and �捥,EGI) differed more insignificantly with the increase of Qg. In addition, the value of �捥,EGI was reduced because bubble-coalesced phenomenon occurred more significantly with the increasing Qg. As a whole, liquid hold-up (�掞) was increased with increasing liquid superficial velocity (ul), while the solids hold-up (�掫) and gas hold-up (�捥) was decreased. The bed height was increased with the increase of volumetric loading rate because of a larger ���|�n Under the condition of external gas injection, bed contraction was occurred because of bubbles coalesced, especially at high Qg. Furthermore, the total pressure drop (�嵐t) of AFBR was decreased with the increasing Qg. At the same ul, value of �嵐t of internal biogas production was the lowest, comparing with those of two other conditions (without biogas and external gas injection).
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