Bench-scale Tank Research Articles

Remediation of BTEX plume in a continuous flow model using zeolite-PRB

Adsorption is a well-known phenomenon that causes the remediation of BTEX (Benzene, Toluene, Ethylbenzene, and Xylene). Zeolite is typically useful for the removal of BTEX from groundwater. In this study, the migration of the BTEX plume was investigated in a bench-scale tank model as a shallow aquifer. The objective of this research was to analyze the performance of a natural zeolite in-situ PRB remediation technique. Natural zeolite was applied as a physical permeable reactive barrier. In the first part of the experiment, 40 ml of BTEX as a contaminant was injected at the injection point (BI) into the sand tank. Samples were taken periodically via 14 boreholes for BTEX test for 23 days and analyzed using a GC-FID instrument. The results indicated high removal rates of BTEX by passing through the zeolite barrier. Zeolite barrier reduced the BTEX concentration up to 90% of the initial value. However, the barrier efficiency started to decrease after 132 h since pollution injection reached a minimum amount (%53 of the initial value) due to occupying the free space and grain pore where BTEX was adsorbed onto the surface of zeolite, thereby decreasing the barrier efficiency.

Operation of a bench-scale TiFe-based alloy tank under mild conditions for low-cost stationary hydrogen storage

Activation processes of 55 kg TiFe-based alloy, filled in a conventional bench-scale tank (TiFe-based tank) under 1.0 MPa Gauge and at 80 °C, and its hydrogen absorption and desorption properties were studied. Following six ab/desorption cycles, the activation process was completed after the seventh absorption process. A long operating time (284 h) was necessary to complete the activation treatment. However, the operating time could be shortened by optimizing each activation process. At a constant hydrogen flow rate of 20 NL/min, the TiFe-based tank absorbed and desorbed >8 Nm3 hydrogen at inlet brine temperatures of 60 °C and 70 °C, respectively. Heat exchange between the alloy bed and the brine circulation during desorption processes was about two times higher than during the absorption processes. Compared with 70 kg LaNi5 filled in the same tank (LaNi5 tank), the heat exchange was higher. This shows the TiFe-based tank would be more suitable for high hydrogen flow operations than the LaNi5 tank.

Model based evaluation of a contaminant plume development under aerobic and anaerobic conditions in 2D bench-scale tank experiments

The influence of transverse mixing on competitive aerobic and anaerobic biodegradation of a hydrocarbon plume was investigated using a two-dimensional, bench-scale flow-through laboratory tank experiment. In the first part of the experiment aerobic degradation of increasing toluene concentrations was carried out by the aerobic strain Pseudomonas putida F1. Successively, ethylbenzene (injected as a mixture of unlabeled and fully deuterium-labeled isotopologues) substituted toluene; nitrate was added as additional electron acceptor and the anaerobic denitrifying strain Aromatoleum aromaticum EbN1 was inoculated to study competitive degradation under aerobic /anaerobic conditions. The spatial distribution of anaerobic degradation was resolved by measurements of compound-specific stable isotope fractionation induced by the anaerobic strain as well as compound concentrations. A fully transient numerical reactive transport model was employed and calibrated using measurements of electron donors, acceptors and isotope fractionation. The aerobic phases of the experiment were successfully reproduced using a double Monod kinetic growth model and assuming an initial homogeneous distribution of P. putida F1. Investigation of the competitive degradation phase shows that the observed isotopic pattern cannot be explained by transverse mixing driven biodegradation only, but also depends on the inoculation process of the anaerobic strain. Transient concentrations of electron acceptors and donors are well reproduced by the model, showing its ability to simulate transient competitive biodegradation.

Effect of Some Fermentation Parameters on Ethanol Production from Beet Molasses by <i>Saccharomyces cerevisiae</i> CAIM13

Problem Statement: Some component of fermentation medium showed to reduce the Saccharomyces cerivisae production of ethanol. Approach: This study was designed to evaluate the role of some fermentation parameters in affecting ethanol productivity from beet molasses BM by Saccharomyces cerevisiae CAIM13. Results: Increase in cell concentration (inoculums size) of the yeast above 3.6×105 cells/100 mL decreased the ethanol yield. The yeast could tolerate ethanol concentration up to 10% but failed to grow at concentration of 12 and 15%. Employment of a bench-scale tank fermenter enhanced the fermentation efficiency. 77% of BM sugars were assimilated after 48h giving a concentration of 5.4% ethanol. Utilization of a cell-recycling technique showed that the tested organism was capable of performing four fermentation cycles. The mud-free, H2SO4-treated beet molasses TBM was superior to sucrose in the repeated batch fermentation technique. A continuous-flow fermentation technique employing immobilized yeast cells yielded maximum ethanol productivity after 6 days. Conclusion: The present investigation has demonstrated the importance of some fermentation parameters in improving the alcoholic fermentation technology of BM. When free cells of S. cerevisiae. In the case of immobilized cells, the continuous-flow technique speared superior to the repeated batch-fermentation technique in production of alcohol from TBM.

A CFD model for predicting the flow patterns of viscous fluids in a bioreactor under various operating conditions

Computational fluid dynamics simulation is becoming an increasingly useful tool in the analysis and design of simultaneous saccharification fermentation (SSF) and saccharification followed by fermentation process (SFF). To understand and improve mixing and mass transfer in a highly viscous non-Newtonian system, it was necessary to simulate the flow behavior in this bench scale bioreactor (BioFlo 3000). This study focused on designing a high concentration medium agitation system for such a process using the commercial computational fluid dynamics package Fluent (V. 6.2.20) and its preprocessor Mixsim (V. 2.1.10). The objective of this study is to compare performance of various designs of a bioreactor and identify the flow pattern and related phenomena in the bench scale tank. The configuration of the physical model for simulating a mixing tank with a Rushton impeller consists of an ellipsoidal cylindrical tank with four equally spaced wall mounted baffles extending the vessel bottom to the free surface, stirred by a centrally located six-blade Rushton turbine impeller. Simulations were performed with the original and a modified design in which the lower bottom shaft mounted a Lightnin A200 impeller. The results suggest that there is a potential for slow or stagnant flow between top impellers and bottom of the tank region, which could result in poor nitrogen and heat transfer for highly viscous fermentations. The results also show that the axial velocity was significantly improved for the modified geometry in the bottom of the tank.

Effect of some fermentation parameters on ethanol production from beet molasses by Saccharomyces cerevisiae Y-7

This investigation was designed to evaluate the role of some fermentation parameters in affecting ethanol productivity from beet molasses (BM) by Saccharomyces cerevisiae Y-7. Increase in cell concentration (inoculum size) of the yeast above 3·6×105 cells/100 ml decreased the ethanol yield. The yeast could tolerate ethanol concentration up to 10% but failed to grow at concentrations of 12 and 15%. Employment of a bench-scale tank fermenter enhanced the fermentation efficiency; 77% of BM sugars were assimilated after 48 h giving a concentration of 5·4% ethanol. Utilization of a cell-recycling technique showed that the test organism was capable of performing 4 fermentation cycles. The mud-free, H2SO4-treated beet molasses (TBM) was superior to sucrose in the repeated batch fermentation technique. A continuous-flow fermentation technique employing immobilized yeast cells yielded maximum ethanol productivity after 6 days.

Effects of orifice size and surface conditions on oxygen transfer in a bench scale diffused aeration system

Abstract Non‐steady state gas transfer methodology was used to examine the effect of orifice size and surface conditions on the rate of oxygen transfer in a 239 L bench scale tank. Each orifice size tested (40 μ, 397 μ and 1588 μ) increased the overall oxygen transfer coefficient (KLa20, hr−1) ; standard oxygen transfer rate (OTs, g O2/hr) ; transfer efficiency (Eo, %) and energy efficiency (Ep/ g O2/kW‐hr) as orifice diameter decreased. The three surface conditions examined exerted a minor effect on oxygen transfer.