Varma Rajneesh, Al-Dahhan Muthanna
Bioreactors and Bioprocess Engineering Laboratory, Chemical Reaction Engineering Laboratory, Department of Energy Environmental and Chemical Engineering, Washington University, St. Louis, Missouri 63130, USA.
Biotechnol Bioeng. 2007 Dec 15;98(6):1146-60. doi: 10.1002/bit.21500.
The effects of sparger design and gas flow rate on, gas holdup distribution and liquid (slurry) recirculation velocity have been studied in a surrogate anaerobic bioreactor used for treating bovine waste with a conical bottom mixed by gas recirculation. A single orifice sparger (SOS) and a multi-orifice ring sparger (MORS) with the same orifice open area and gas flow rates (hence the same process power input) are compared in this study. The advanced non-invasive techniques of computer automated tomography (CT) and computer automated radioactive particle tracking (CARPT) were employed to determine gas holdup, liquid recirculation velocity, and the poorly mixed zones. Gas flows (Q(g)) ranging of 0.017 x 10(-3) m(3)/s to 0.083 x 10(-3) m(3)/s were used which correspond to draft tube superficial gas velocities ranging from 1.46 x 10(-2) m/s to 7.35 x 10(-2) m/s (based on draft tube diameter). Air was used for the gas, as the molecular weights of air and biogas (consisting mainly of CH(4) and CO(2)) are in the same range (biogas: 28.32-26.08 kg/kmol and air: 28.58 kg/kmol). When compared to the SOS for a given gas flow rate, the MORS gave better gas holdup distribution in the draft tube, enhanced the liquid (slurry) recirculation, and reduced the fraction of the poorly mixed zones. The improved gas holdup distribution in the draft tube was found to have increased the overall liquid velocity. Hence, for the same process power input the MORS system performed better by enhancing the liquid recirculation and reducing the poorly mixed zones.
在一个用于处理牛粪的替代厌氧生物反应器中，研究了气体分布器设计和气体流速对气体滞留分布和液体（浆液）再循环速度的影响，该反应器底部为锥形，通过气体再循环进行混合。本研究比较了具有相同孔口开放面积和气体流速（因此具有相同的过程功率输入）的单孔气体分布器（SOS）和多孔环形气体分布器（MORS）。采用先进的非侵入性技术，即计算机自动断层扫描（CT）和计算机自动放射性粒子跟踪（CARPT），来确定气体滞留率、液体再循环速度和混合不良区域。使用的气体流量（Q(g)）范围为0.017×10⁻³ m³/s至0.083×10⁻³ m³/s，这对应于导流管表观气体速度范围为1.46×10⁻² m/s至7.35×10⁻² m/s（基于导流管直径）。气体使用空气，因为空气和沼气（主要由CH₄和CO₂组成）的分子量在相同范围内（沼气：28.32 - 26.08 kg/kmol，空气：28.58 kg/kmol）。与给定气体流速下的SOS相比，MORS在导流管中具有更好的气体滞留分布，增强了液体（浆液）再循环，并减少了混合不良区域的比例。发现导流管中改善的气体滞留分布增加了整体液体速度。因此，在相同的过程功率输入下，MORS系统通过增强液体再循环和减少混合不良区域表现得更好。
