Effect of sparger design on hydrodynamics of a gas recirculation anaerobic bioreactor

Abstract

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.

Local time-averaged gas holdup in fluidized bed reactor using gamma ray computed tomography technique (CT)

“…The CT used in this study was based on a newer generation of double fan-beam scanning configuration. Details on both the hardware and the software used in this study have been described by Varma and Al-Dahhan [11], Varma et al [12]. A photograph of the CT facility used in this study is pictured in Fig.…”

“…The reconstruction algorithm proposed and used by Varma and Al-Dahhan [11], Varma et al [12] was implemented to reconstruct the cross-sectional distribution of relative attenuation in a two-phase system. We proposed an alternating minimization (AM) algorithm based on turning a maximum likelihood problem into a double minimization of I-divergence introduced by Csiszár [13].…”

Experimental investigation of pebble flow dynamics using radioactive particle tracking technique in a scaled-down Pebble Bed Modular Reactor (PBMR)

“…In general, the RPT technique uses a single or multiple radioactive particles (also called as a tracer) emitting γ-rays (i.e. radiotracer particle) whose motion is followed in the 3-D domain of the whole system using either collimated or non-collimated scintillation detectors [12][13][14]. In the RPT technique used in this work (Figure 2), the instantaneous tracer position was identified by simultaneously monitoring photo-peak counts received by a set of non-collimated sodium iodide (NaI) scintillation detectors which were arranged strategically around the system [15][16][17][18].…”

Computational fluid dynamics modeling of mass transfer behavior in a bioreactor for hairy root culture. I. Model development and experimental validation

“…Computational fluid dynamics (CFD), a powerful tool to investigate multiple‐phase flow, has been widely used to aid bioreactor design and process optimization in the culture process of microorganisms, mammalian cells, and plant cells 15–22. This work aims to develop a two‐dimensional axisymmetric CFD model with a porous media model and discrete population balance model (PBM) to address the complex fluid hydrodynamics and mass transfer behavior in the hairy root bioreactor culture.…”