Search

The present paper provides a complete databank of bubble plume hydrodynamics in various media characterized by different viscosities in the range 1 – 100 mPa . s . Thus, the influence of the viscosity on bubble plume oscillations and on both liquid and gas velocity fields is studied. The role of the bubble size distribution at different viscosities was also analysed by using two different spargers: a membrane to create ellipsoidal millimetrice bubbles and a slugflow tube to create spherical cap bubbles. Mean velocity profiles, averaged over a large number of plume oscillation periods and corresponding root mean square profiles are discussed, in both phases. Furthermore, void fraction profiles, plume oscillation periods, and bubble size distributions are given for all experimental conditions. Finally, probability density functions and phase averaged profiles in the liquid phase provide additional information. The dependence of bubble plume hydrodynamics on liquid viscosity is huge. At large viscosity, the oscillating plume is damped, regardless of the sparger. Concerning the membrane sparger the viscosity increase modifies the plume oscillation period and its lateral plume expansion, whereas, in the case of the slugflow sparger, only the plume expansion is impacted. Liquid phase hyrdodynamics are weakly affected by the choice of sparger, especially at high viscosities.

It is known that the performances of multi-phase reactors depend on the operating parameters (the temperature and the pressure of the system), the phase properties, and the design parameters (the aspect ratio (AR), the bubble column diameter, and the gas sparger design). Hence, the precise design and the correct operation of multi-phase reactors depends on the understanding and prediction of the fluid dynamics parameters. This paper contributes to the existing discussion on the effect of operating and design parameter on multi-phase reactors and, in particular, it considers an industrial process (e.g., the LOPROX (low pressure oxidation) case study, which is typical example of two-phase bubble columns). Based on a previously-validated set of correlations, the influence of operating and design parameter on system performances is studied and critically analyzed. First, we studied the effects of the design parameter on the liquid-gas interfacial area, by keeping constant the fluid physical-chemical properties as well as the operating conditions; subsequently, we discussed for a fixed system design, the influence of the liquid phase properties and the operating pressure. In conclusion, this paper is intended to provide guidelines for the design and scale-up of multi-phase reactors.

Although column flotation cells have been extensively studied in the literature, the hydrodynamic impact of orifice properties has not been adequately addressed yet. This paper initially investigat...

Bubble sparging has been used to supply oxygen to large-scale bioreactor systems. However, sparged bubbles cause cell death by rupturing due to shear stress, and the foam layer carries a risk of contamination. Large-scale culture of human induced pluripotent stem cells (hiPSCs) is required for manufacturing, but hiPSCs show high sensitivity to shear stress, and also, aseptic processing is important for their expansion. In this study, a culture system with bubble sparging for hiPSC proliferation was designed using a plastic fluid as a culture medium. The rising bubble velocity in the plastic fluid decreased and was lower than that in a Newtonian fluid when the time interval between bubbles generation, Δt, was greater than 0.14 s. Under this condition, aggregate distribution in the plastic fluid was maintained without liquid flow. Although large aeration induced aggregate coalescence and growth inhibition, the apparent specific growth rate at Δt > 0.14 s increased with an increase in the aeration rate, and the maximum value was similar to that of the conventional suspension culture in a stirred bioreactor system. The gas hold-up in the plastic fluid was higher than that in a Newtonian fluid because of the lower rising bubble velocity, which leads to the suppression of bubble sparging. Therefore, our results indicated that using a plastic fluid leads to a more efficient oxygen supply without agitation in a spatial–temporal phase-transition culture system.

Three designs of static spargers were used in a pilot scale external loop airlift reactor to determine their effects on the gas holdup and mass transfer characteristics for an air-water system. Although previous studies involving the effects of sparger design on gas holdup and mass transfer have been reported, no comparative investigations using different spargers in the same pilot scale external loop airlift reactor have been done. In this investigation, the results show that the perforated plate sparger (A) was the best design and produced the best overall gas holdup and mass transfer values when compared to a perforated disk sparger (B) and perforated pipe sparger (C). The perforated pipe sparger produced the worst gas holdup and mass transfer values and also had the worst overall performance for bubble size, flow and distribution. This investigation emphasises the importance of sparger design and that it must be considered in the overall design of an airlift reactor as it has a significant influence on the gas holdup and mass transfer characteristics.

In order to the intensification of gas-liquid mass transfer of MDEA-containing wastewater during wet air oxidation process (WAO), the microbubbles and millimeter bubbles were applied by fine-pore sparger (5μm and 20-30 μm) and single pore sparger (6.35mm), respectively. Effect of the superficial gas velocity on the average microbubble size, gas holdup and oxygen mass transfer coefficient (KLa) of MDEA-containing wastewater at the ambient conditions was studied. The results showed that the microbubbles (less than 1 mm) were beneficial to enhance mass transfer process and had the higher dissolved oxygen concentration during WAO process of MDEA-containing wastewater owing to higher gas holdup and larger oxygen mass transfer coefficient. The COD removal ratio was 66% at low superficial gas velocity (ug=0.3 cm/s) in wet air oxidation process by microbubbles, while it achieved at high superficial gas velocity (ug=3.0cm/s) by millimeter bubbles. The critical oxygen mass transfer coefficient KLa was 0.183 min-1 of MDEA-containing wastewater by 20-30 μm and 5 μm fine pore sparger, which was 2∼5 times more than that of single pore sparger (

Sparging-based methods have long been used to liberate volatile organic compounds (VOCs) from liquid sample matrices prior to analysis. In these methods, a carrier gas is delivered from an external source. Here, we demonstrate "catalytic oxygenation-mediated extraction" (COME), which relies on biocatalytic production of oxygen occurring directly in the sample matrix. The newly formed oxygen (micro)bubbles extract the dissolved VOCs. The gaseous extract is immediately transferred to a separation or detection system for analysis. To start COME, dilute hydrogen peroxide is injected into the sample supplemented with catalase enzyme. The entire procedure is performed automatically-after pressing a "start" button, making a clapping sound, or triggering from a smartphone. The pump, valves, and detection system are controlled by a microcontroller board. For quality control and safety purposes, the reaction chamber is monitored by a camera linked to a single-board computer, which follows the enzymatic reaction progress by analyzing images of foam in real time. The data are instantly uploaded to the internet cloud for retrieval. The COME apparatus has been coupled on-line with the gas chromatography electron ionization mass spectrometry (MS) system, atmospheric pressure chemical ionization (APCI) MS system, and APCI ion-mobility spectrometry system. The three hyphenated variants have been tested in analyses of complex matrices (e.g., fruit-based drinks, whiskey, urine, and stored wastewater). In addition to the use of catalase, COME variants using crude potato pulp or manganese(IV) dioxide have been demonstrated. The technique is inexpensive, fast, reliable, and green: it uses low-toxicity chemicals and emits oxygen.

The performance of the different configurations of AnMBRs is affected by operating parameters including solid retention time (SRT), hydraulic retention time (HRT), organic loading rate (OLR), sludge recycle rate, temperature and wastewater characteristics. Generally, the optimum operating condition is characterized by a longer SRT and HRT, higher OLR at a mesophilic temperature range. These parameters also affect the propensity of membrane fouling which is considered as the major challenge limiting its sustainable use. Hence, these parameters need to be understood and optimized. The common fouling control strategies include sub-critical flux operation, membrane relaxation, backwashing, biogas sparging, sludge recycle and use of coagulants and turbulence promoters are inadequate in fully controlling the fouling process. Hence, new and emerging technologies like enzymatic or bacterial degradation through quorum quenching technology are being explored. Moreover, integration of rotary disks/membrane, attached growth system, dynamic membrane, electrochemical membrane and baffled reactor configurations are introduced as modifications to the conventional AnMBR. Review of these strategies reveal that these novel configurations of AnMBR and the use of quorum quenching technology offer a potential sustainable approach to fouling control, and hence should be explored further.

The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor (JBR) including the gas holdup, volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature, pH and superficial gas velocity. The reactor diameter and height were 11 and 30 cm, respectively. It was equipped with a single sparger, operating at atmospheric pressure, 20 and 40 °C, and two pH values of 3 and 6. The height of the liquid was 23 cm, while the superficial gas velocity changed within 0.010–0.040 m·s−1 range. Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase. The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution. The gas holdup was calculated based on the liquid height change, while the specific interfacial area was obtained by a physical method based on the bubble size distribution (BSD) in different superficial gas velocities. The results indicated that at the same temperature but different pH, the gas holdup variation was negligible, while the liquid-side volumetric mass transfer coefficient at the pH value of 6 was higher than that at the pH = 3. At a constant pH but different temperatures, the gas holdup and the liquid-side volumetric mass transfer coefficients at 40 °C were higher than that of the same at 20 °C. A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient (kla) in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs.

This work presents the influence of the sparger opening area, gas velocity, and bubble size on hydrodynamics and transition of the flow regime from uniform to re-circulatory in a rectangular bubble column using OpenFOAM. In the course of development of the model, the effect of several drag closures and lift on the predictability of the CFD model was studied by comparing the predictions with published experimental results. Reynolds number-based drag closure was found to be suitable for uniform sparger whereas Tsuchiya drag (Tsuchiya et al. in Chem Eng Sci 52:3053–3066, 1997. https://doi.org/10.1016/S0009-2509(97)00127-9) was used to simulate gas–liquid flow for other spargers. Simulations were performed for seven different spargers with opening area 18–100% (superficial gas velocity of 2.9–5.8 cm/s) and bubble size of 2–8 mm. The smaller opening area and higher gas velocity promote the re-circulatory flow in the bubble column. Change in bubble size affects the hydrodynamics due to change in lift and drag forces.

The macromolecule oligo(poly(ethylene glycol) fumarate) (OPF) exhibits promising attributes for creating suitable three-dimensional hydrogel environments to study cell behavior, deliver therapeutics, and serve as a degradable, nonfouling material. However, traditional synthesis techniques are time consuming, contain salt contaminants, and generate significant waste. These issues have been overcome with an alternative, one-pot approach that utilizes inert gas sparging. Departing from previous synthetic schemes that require acid scavengers, inert gas sparging removes byproducts in situ, eliminating significant filtration and postprocessing steps, while allowing a more uniform product. Characterized by nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry, nitrogen sparge synthesis yields an OPF product with greater polymer length than traditional acid scavenger synthesis methods. Furthermore, nitrogen-sparged OPF readily crosslinks using either ultraviolet or thermal initiator methods with or without the addition of short-chain diacrylate units, allowing for greater tunability in hydrogel properties with little to no cytotoxicity. Overall, inert gas sparging provides a longer chain and cleaner polymer product for hydrogel material studies while maintaining degradable characteristics. IMPACT STATEMENT: Using nitrogen sparging, we have demonstrated that oligo(poly(ethylene glycol) fumarate) (OPF) can be produced with decreased postprocessing, increased product purity, greater oligomerization, and cell viability. These properties lead to greater tunability in mechanical properties and a more versatile hydrogel for biomedical applications. The simplification of synthesis and elimination of impurities will expand the utility of OPF as a degradable hydrogel for cell culture, tissue engineering, regenerative medicine, and therapeutic delivery, among other applications.

At present, the development and optimization of methods to eliminate the consequences of soil contamination with hydrocarbons is gaining increasing economic and social importance; it is the basis for sustainable development of the oil industry. Within the frames of the scientific research, a review of literature was carried out in the sphere of utilization of organic wastes from the food industry in reclamation of oil-contaminated soils; an experimental study of efficiency of the use of wastes from the brewing industry in the process of bioremediation of oil-contaminated soils was conducted and phytotoxicity of these wastes was determined. Experimental research was conducted at different initial concentrations of oil in the soil, which allowed to establish the optimal range of oil pollution level at which the efficiency of brewing waste use is the highest. Thus, at low concentrations (1000-2000 mg/kg), the dynamics of oil concentration decrease in the soil remained preserved throughout the whole duration of the experiment, and the efficiency of oil destruction in the soil exceeded 98%, which confirmed the overall efficiency of application of brewing waste for reclamation of oil-contaminated soils.

A gas–liquid swirling-sparger (GLSS) configured along a toroidal distributor was developed based on swirling flow to enhance the efficiency of gas–liquid contacting. Gas–liquid contacting was visua...

In this study, a novel gas sparging regime was applied, in which filtration was conducted without gas sparging to create a pseudo dead-end (DE) filtration cycle followed by membrane relaxation/backwashing for a short period of time with gas sparging until the TMP set-point was achieved. Compared with conventional continuous filtration and continuous gas sparging (CGS) modes and temporal pseudo DE filtration modes, this pseudo DE filtration coupled with TMP set-point control mode can achieve lower energy demand with sustainable membrane operation. The impacts of the TMP set-point value, imposed flux and physical cleaning process (membrane relaxation/backwash coupled with gas sparging) were evaluated. The result indicated that a moderate TMP set-point value (10–12 kPa) should be selected. Backwashing can significantly reduce the irreversible fouling and enhance the net permeate flux. However, when the TMP set-point value was higher (TMPset = 14 kPa), severe cake layer consolidation occurred and no appreciable improvement of fouling control was observed even with backwashing coupled with gas sparging. The optimum condition can be established when the TMP set-point value was 12 kPa at a flux of 15 L m−2 h−1 in terms of a higher net flux and lower specific energy demand. Importantly, sustainable membrane operation can be achieved under pseudo DE filtration coupled with TMP set-point control mode with a low energy demand (0.09 kWh m−3) and low operational cost ($0.027 per m3), promoting energy neutral municipal wastewater treatment to be realized.

LNG gas-turbine engines have several advantages over diesel engines: capacity to develop higher power with smaller weight and size, lower fuel price, environment friendliness, etc. At the same time, this type of engines is characterized by low efficiency at insufficient load and high idle-run fuel consumption. A part of the energy losses under these conditions occurs in the cryogenic unit of the LNG gas-turbine engine fuel system. Schematic diagrams and characteristic features of the cryogenic unit of the LNG gas-turbine engine are presented. Schemes of LNG delivery with vapor-pressurization, sparging of the tank with an external noncondensing gas, and use of pumps are described. The impact on the fuel system performance of such factors as fuel delivery mode, LNG flow return, restraining temperature of the delivered LNG, variation of LNG composition, etc. are investigated. The criteria of efficiency of the system in start, main, and idle modes are calculated by mathematical modeling method.

Membrane fouling behaviors were investigated to different biogas sparging flows such as 0.5, 1.0, and 1.5 L biogas/min for anaerobic submerged membrane bioreactor (AnSMBR) treating synthetic wastewater in a laboratory-scale. For each different biogas flow rate, the membrane module of the same feature was used in the system and the effect of biogas sparging flow on fouling control was examined in the process. Surface area of the used membrane module was selected as 162.6 cm(2). The sprarging biogas was supplied from the gas formed in reactor system. Treatment parameters were analyzed in the process of reactor operation. Also, a series of analysis, including soluble microbial products (SMP), extracellular polymeric substances (EPSs), scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, and filtration resistances were performed by considering the membrane module. The AnSMBR accomplished COD removal efficiencies between 95 and 98%. Total organic carbon and sulfate concentration in permeate were found in the range of 25-56 and 90-200 mg/L, and 96-98 and 38-65% in removal percentage; respectively. TSS and VSS concentrations in permeate were less than 10 mg/L that means removal efficiencies of 98%. Methane production rate in the system was determined of 0.35 +/- 0.08 LCH4/g COD removed. The results showed that differences between COD and TOC removals were negligible at different biogas sparging flows. The priority of biogas sparging flows in terms of providing high permeate fluxes were found to be 1.5 L biogas/min > 1.0 L biogas/min > 0.5 L biogas/min. The same order was found with the fluxes in terms of both SMP and EPS within cake formed on the fibers in membrane module. Studying results showed that biogas sparging flow increasing was found to effective on membrane fouling controls. It has been determined that sparging gas at an optimum flow rate (1.0 L biogas/min) can be effective in controlling membrane fouling.

This work mainly aims on the investigation of phase hold-up characteristics in a column flotation at different feed solid concentrations performing for an extensive range of working conditions. Phase hold-ups are measured using the electrical resistance tomography (ERT) coupled with pressure transducers technique. Experiments are conducted for two different nature mineral particles: hydrophilic (silica) and semi-hydrophobic (oxidized coal). The impact of gas superficial velocity, feed superficial velocity and pulp slurry height for a fixed sparger and frother addition on the gas and solid dispersion are studied. Gas hold-up increases with the gas flowrate and slurry feed rate, decreases with solid concentration. Further, bubble dynamics is estimated using coupled ERT with dynamic gas disengagement (DGD) approach. It is found that the solid’s presence affect the bubble swarm velocity thereby causing local gas holdup to drop. Possible mechanisms due to solid particles on gas dispersion are discussed and verified in the light of current experimental results.

Operations involving gas–liquid agitated vessels are common in the biochemical and chemical industry; ensuring good contact between the two phases is essential to process performance. In this work, a methodology to compute acoustic emission data, recorded using a piezoelectric sensor, to evaluate the gas–liquid mixing regime within gas–liquid and gas–solid–liquid mixtures was developed. The system was a 3L stirred tank equipped with a Rushton Turbine and a ring sparger. Whilst moving up through the vessel, gas bubbles collapse, break or coalesce generating sound waves transmitted through the wall to the acoustic transmitter. The system was operated in different flow regimes (non-gassed condition, loaded and complete dispersion) achieved by varying impeller speed and gas flow rate, with the objective to feed machine learning algorithms with the acoustic spectrum to univocally identify the different conditions. The developed method allowed to successfully recognise the operating regime with an accuracy higher than 90% both in absence and presence of suspended particles.

In this study, a modified gas feeding bubble column photo-bioreactor was utilized for microalgae cultivation and CO2 capturing. By applying response surface methodology, the optimum values of temperature, pH, light intensity, aeration rate, light-dark cycle and time were determined as 25 ° C, 8, 2700 lx, 0.5 LPM and 16−8 h, respectively. Two air spargers (with different aperture size) were used to study the effect of the bubble size on the CO2 removal and microalgae growth rate. Besides, the inlet air was humidified to avoid the evaporation from the photo-bioreactor. For the smaller bubbles and 7% CO2 concentration, the maximum values for the CO2 fixation rate, productivity and concentration of microalgae were determined to be 633.73 mg L−1d−1, 337 mg L−1d−1 and 4244 mg L−1, respectively. CO2 utilization efficiency was 35% for the smaller bubbles, showing a 15% increase over that for the larger bubbles.

It is known that changes in geochemical fields may be due to the formation and development of earthquake foci. Hydrogeochemical fields at observation sites can be disturbed by underground shocks of sufficient energy, which occur at specific epicentral distances. Our study aimed to reveal these relationships by analysing the concentrations of helium and radon in groundwaters of Southern Pribaikalie, the area around Lake Baikal in Russia. Water samples were taken daily at 10 a.m. from artesian well No. 3 in Zeleny Mys, Irkutsk region. After water sparging, radon concentrations were measured by beta-detection Camera-01 and INGEM-1 (magnetic discharge indicator of helium) to determine helium concentrations. We analysed the concentration values in connection with 22 seismic events that occurred from 2010 to 2016 at the hydrogeochemical observation site (energy classes K of 10.4–14.5; epicentral distances of 40–750 km; conditional energy of K’>6). Based on the radon and helium concentration diagrams, specific regularities were established in the concentration variations before the earthquakes. Generally, concentration variations (increasing/decreasing) in excess of 1.5–2.0 standard deviations preceded earthquakes. This article presents the study results and discusses variations in the radon and helium concentrations, which are due to the seismic process and can be considered as a short-term precursor of earthquakes.

A comprehensive experimental study of the hydrodynamic behaviors for the specific system of air/paraffin oil/silica particles in a slurry bubble column of 0.15 m diameter and 2.9 m length has been carried out. The effect of regime transition, solid concentrations, static liquid height, sparger type and related bubble size on gas holdup over a range of superficial gas velocities has been investigated. From the experimental work, it is revealed that the gas holdup increases by increasing the superficial gas velocity and transition regime occurred at 0.043 to 0.08 m/s. The slope of this curve is steeper for homogeneous regime and less for heterogeneous regime. In addition, the presence of silica particle (0–40 vol %) inhibits bubble breakage, increases rise velocity and consequently decreases residence time and gas holdup. Approximately a 40% decrease in the overall gas holdup was observed by adding 40% solid particles to the air/paraffin oil system. Moreover, increasing static liquid height from 6 to 12 leads to about a 61% decrease in gas holdup in the absence of solid particles. Also, the use of a perforated plate instead of a porous one causes a 9% increase and a 21% decrease in bubble size and gas holdup, respectively. Finally, it is found that the Krishna and Sie correlation can predict gas holdup in the air/paraffin oil/silica particles system with an acceptable minimum relative error of about 8%.

Mass transfer is known to play a critical role in bioprocess performance and henceforth monitoring dissolved O2 (DO) and dissolved CO2 (dCO2) is of paramount importance. At bioreactor level these parameters can be monitored online and can be controlled by sparging air/oxygen or stirrer speed. However, traditional small‐scale systems such as shake flasks lack real time monitoring and also employ only surface aeration with additional diffusion limitations imposed by the culture plug. Here we present implementation of intensifying surface aeration by sparging air in the headspace of the reaction vessel and real‐time monitoring of DO and dCO2 in the bioprocesses to evaluate the impact of intensified surface aeration. We observed that sparging air in the headspace allowed us to keep dCO2 at low level, which significantly improved not only biomass growth but also protein yield. We expect that implementing such controlled smart shake flasks can minimize the process development gap which currently exists in shake flask level and bioreactor level results., Surface aeration intensification was implemented in shake flasks enabled with in house developed monitoring sensors for pH, dissolved oxygen and dissolved CO2. Efficient removal of CO2 from the shake flasks and enhanced O2 supply resulted in increased biomass growth and protein yield. Improved surface aeration in shake flasks can translate into better scale down models and smoother scale up activities, and thus will bridge the gap that exists in process development.

The present study investigated the effect of light intensity and mixing on microalgae growth in a raceway by comparing the performance of a paddlewheel to a combination of paddlewheel and CO2 spargers in a 20 L raceway. The increase of light intensity was known to be able to increase the microalgal growth rate. Increasing paddlewheel rotation speed from 13 to 30 rpm enhanced C. vulgaris growth by enhancing culture mixing. Simulation results using computational fluid dynamics (CFD) indicated that both the turnaround areas of the raceway and the area opposite the paddlewheel experienced very low flow velocities (dead zones) of less than 0.1 m/min, which could cause cell settling and slow down growth. The simulated CFD velocity distribution in the raceway was validated by actual velocity measurements. The installation of CO2 spargers in the dead zones greatly increased flow velocity. The increase of paddlewheel rotation speed reduced the dead zones and hence increased algal biomass production. By complementing the raceway paddlewheel with spargers providing CO2 at 30 mL/min, we achieved a dry cell weight of 5.2 ± 0.2 g/L, which was about 2.6 times that obtained without CO2 sparging.

Empirical and theoretical aspects of non-catalytic molten sulfur degassing as one of the vital actions in Claus Unit have been investigated in this article. A laboratory bubble column has been set up to study the hydrodynamic behavior of gas-liquid system. Values of gas holdup were also compared with predictions of some correlations in the case of application of porous spargers. The mathematical model of degassing was also developed considering reaction of H2S with sulfur molecules in the molten sulfur and generation of H2Sx species. The experimentally-measured parameters of gas holdup and bubble size were used in the mathematical model. Other parameters including Henry’s law constant of H2S-liquid sulfur system and reaction rate constants were obtained from published formulas presented by Marriott and Ji, respectively. The obtained results were compared to the empirical data of non-catalytic degassing performed in the laboratory setup. Reasonable compatibility was observed between the model-derived and experimental results. The results showed a fast removal of dissolved H2S within few minutes, followed by very slow removal of H2Sx through its chemical conversion to H2S and its purging by sweep gas. The novel gas holdup profile and images presented in this article show interesting features of hydrodynamic behavior of molten sulfur.

The response surface methodology has been applied to study reversible and irreversible fouling rates caused by anaerobic sludge in membrane bioreactors, with the aim of controlling membrane fouling by adjusting filtration conditions. The challenge of obtaining statistically significant results of long-term fouling by means of mid-term assays has been addressed. The individual and combined effects of the filtration flux, backwashing intensity, gas sparging and crossflow velocity on membrane fouling, were analyzed in two types of membranes: an external tubular membrane and a submerged hollow fiber membrane. In the external membrane, the reversible fouling rate was as low as 0.27 ± 0.10 mbar/min, depending mainly on the filtration flux and gas sparging. However, the principal control parameter of the irreversible fouling rate was the crossflow velocity, reaching 2.12 ± 1.75 1012 m−2 in terms of increase of resistance per cubic meter filtered by square meter of membrane. In the submerged membrane, the irreversible fouling rate was quite lower, 0.78 ± 0.40 mbar/d, despite the reversible fouling rate was higher, 1.26 ± 0.42 mbar/min. In this case, the irreversible fouling depended mainly on the backwashing frequency despite the reversible fouling was more affected by the filtration flux and gas sparging. Hence, the approach used to control the reversible fouling rate does not involve mitigating irreversible fouling on both submerged and external membranes. This study provides a methodological basis for the selection of site-specific operating conditions, under which sustainable operation of membrane bioreactors could be achieved., TCUE 2018–2020 cofounded by European Regional Development Fund (ERDF) and Junta de Castilla y León (Spain) and the inestimable collaboration of Campofrío Frescos and Grupo Ecoalia.

The Steam injection through multi-hole spargers into the pressure suppression pool (PSP) is used in light water reactors to prevent containment over-pressure. The development of thermal stratification in the PSP can reduce its cooling capacity and results in higher containment pressures compared to completely mixed pool conditions. Explicit modelling of direct contact condensation (DCC) of steam at the steam-water interface is a challenge for contemporary codes. Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been proposed to enable the prediction of thermal stratification and mixing transients induced by steam condensation in a large pool. The general idea of the EHS/EMS is to resolve the effect of the DCC phenomena on a large pool, instead of explicit modelling of the small-scale phenomena at steam-water interface. The EHS/EMS models can be implemented using (i) respective boundary conditions at the boundary of the Steam Condensation Region (SCR) or (ii) using source terms in the heat and momentum transport equations. In previous work, EHS/EMS models were implemented using the second approach and validated against data from PPOOLEX and PANDA tests. It was found that results are sensitive to the spatial distribution of the source terms. Since the current data are not sufficient to provide a reasonable distribution, a preliminary study of the first method was done in this paper. The goal of this work is to develop a ‘Unit Cell’ model by using respective boundary conditions for steam injection through multi-hole sparger. The condensed turbulent jet is resolved by introducing the liquid jet with the same effective momentum and heat as the injected steam. A uniform velocity profile solved by EMS model and the temperature boundary solved by EHS model is provided on each injection hole of the sparger wall. Validation is conducted against sparger test in PANDA facilities.

Elemental sulphur is a common fungicide applied in vineyards before harvest, and has been found toincrease the production of desirable polyfunctional mercaptans, but also H2S and unwanted reductivesulphur aroma compounds. This paper investigates the effectiveness of oxygen and nitrogen sparging,applied during fermentation, on the removal of volatile sulphur compounds in Sauvignon blanc wines.Increasing the amount of elemental sulphur added to grapes after pressing, from nil to 10 to 100 mg/L,led to an increase in the formation of 3-mercaptohexanol (3MH), of 3-mercaptohexyl acetate (3MHA) forthe 10 mg/L additions only, and of some unwanted reductive compounds. Few changes were observed inthe concentrations of aroma compounds when the juices were sparged with nitrogen during fermentation.Additions of oxygen during fermentation led to some decrease in the concentration of polyfunctionalmercaptans for the 10 mg/L sulphur additions, but did not significantly remove reductive aroma compounds.Few differences were observed in the concentration of wine phenolics or of further wine aroma familieswith any of the treatments.

The Pressure Suppression Pool (PSP) in a Boiling Water Reactor (BWR) is served as a heat sink to prevent containment over-pressure. The steam can be injected through the multi-hole spargers. The development of thermal stratification where a thermocline with a large temperature gradient appears in the pool can lead to the higher pressure in the dry well compared with completely mixing pool conditions. Prediction of the thermal phenomenon in the pool is necessary for the support of system design and operation. Thus, the Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been proposed. The models can be applied to CFD code by using (i) source terms in the transport equations or (ii) using respective boundary conditions at the Steam Condensation Region (SCR). Previous validation against PPOOLEX and PANDA tests using the source terms approach faced challenges in momentum distribution. Therefore, a preliminary investigation of using the second method was performed. The encouraging results implied that it is possible to further develop this approach. The goal of this work is to further develop the EHS/EMS models for the steam injection through a multi-hole sparger through the SCR model (i.e approach (ii)) and to validate it against the experimental data obtained from PANDA HP5 tests. Modeling guidelines are proposed. The temperature evolutions and vertical velocity profiles of these tests are compared to the simulation results. The agreement suggests that this model can provide an adequate estimation of the pool behavior.

Background: Drastic pH drop is a common consequence of scaling up a mammalian cell culture process, where it may affect the final performance of cell culture. Although CO2 sparging and base addition are used as common approaches for pH control, these strategies are not necessarily successful in large scale bioreactors due to their effect on osmolality and cell viability. Accordingly, a series of experiments were conducted using an IgG1 producing Chinese Hamster Ovary (CHO-S) cell culture in 30 L bioreactor to assess the efficiency of an alternative strategy in controlling culture pH. Methods: Factors inducing partial pressure of CO2 and lactate accumulation (as the main factors altering culture pH) were assessed by Plackett-Burman design to identify the significant ones. As culture pH directly influences process productivity, protein titer was measured as the response variable. Subsequently, Central Composite Design (CCD) was employed to obtain a model for product titer prediction as a function of individual and interaction effects of significant variables. Results: The results indicated that the major factor affecting pH is non-efficient CO2 removal. CO2 accumulation was found to be affected by an interaction between agitation speed and overlay air flow rate. Accordingly, after increasing the agitation speed and headspace aeration, the culture pH was successfully maintained in the range of 6.95-7.1, resulting in 51% increase in final product titer. Similar results were obtained during 250 L scale bioreactor culture, indicating the scalability of the approach. Conclusion: The obtained results showed that pH fluctuations could be effectively controlled by optimizing CO2 stripping.

HBPP uses hot dense bubbles as heat and mass carriers to evaporate the solution with improved evaporation efficiency, compared with the traditional thermal method. To develop an energy efficient water treatment process, we applied combustion gas as inlet gas within HBPP, for the first time to evaporate synthetic seawater. The advantage of using combustion gas is that the hot waste combustion gas from factories can be used at almost no energy cost, thereby reducing energy consumption. In this paper, the evaporation efficiency was determined by measuring the weight loss of column solution of HBPP in a 60 min run. Firstly, the ability of the HBPP to treat different types of wastewater, including 0.5 m NaCl solution or synthetic sewage, was tested by pumping air at the temperature of 80, 120 and 160 °C, respectively. The observed amount of evaporated water vapour was higher for the 0.5 m NaCl solution than for the synthetic sewage at inlet air temperatures of 80 °C and 120 °C but the same at a temperature of 160 °C. The HBPP shows the potential for water treatment regardless of wastewater type. Then, the evaporation efficiency was calculated for both combustion gas and air, at the inlet temperature of 120 °C to evaporate 0.5 m NaCl solution. The result showed an increment of 37% of evaporation efficiency achieved by sparging combustion gas. That is because the contained water vapour has a high capacity for efficient heat transfer to evaporate the solution. As a result, applying combustion gas within HBPP can provide an energy conservative method with improved evaporation efficiency for water treatment.

How to increase foam stability without adding foam stabilizers? As we published earlier, there was more than a sufficient amount of foam stabilizing substances in beer, but these must not be pushed out of the beer surface by foam negative substances. There are several separation steps in a brewing process: lautering, trub separation, and beer filtration; all of these can also separate foam negative substances. This short article discusses how a pH during sparging can influence foam stability. It seems that the lower the pH, the fewer foam negative substances are carried over to the following production steps of a brewing process.

In this study, an advanced noninvasive gamma-ray computed tomography (CT) technique was used for the first time to visualize and quantify the cross-sectional gas holdup distribution of the multiphase flow of an air–water-microalgae system in a cylindrical split airlift photobioreactor. The gas holdup distribution and their radial profiles were investigated during the culturing of the green microalgae Scenedesmus. The gas phase distribution in the entire reactor, including riser region, downcomer region, distribution regions, as well as their distributions above and below the split plate was also characterized, along with the impact of two superficial gas velocities (0.01 and 0.03 m/s), different axial levels, and the changes in the culture from first day until the medium became very dense. The results showed an excellent gas phase distribution in most of the reactor’s regions and had high values around the sparger ring and above the split plate. Moreover, the results indicated that the flow distribution may significantly affect the performance of the photobioreactor, which may have substantial effects on the cultivation process. The results are reliable as benchmark data to validate computational fluid dynamics (CFD) simulations and other models.

The high-speed EDM milling process using hollow tool electrode with high-speed gas flushing inside electrode and high-speed liquid flushing outside electrode is investigated (gas-liquid high-speed EDM). The liquid in electrode outer is used to compress and cool the gas dielectric, which can add to the capacity of expelling the debris and cooling the machining gap for gas dielectric. The high-speed EDM milling experiments were carried out by using gas, liquid, and gas-liquid combinations as the dielectric. Compared with gas EDM, the MRR of gas-liquid EDM can improve 23% and the WOC can reduce 15% with the same SR. Gas-liquid EDM shows advantages over the liquid EDM in reducing 30% SR, 50% WOC, 82% recast layer thickness, and significantly fewer micro-cracks. The flow field simulation results show that the higher pressure in gas-liquid leads to a higher MRR compared with that in gas.

The multi-hole steam ejection system is widely applied in practical engineering applications, whereas the heat transfer mechanisms in unstable condensation conditions are not very clear yet. In this study, the separate-effect mechanism tests of single/double-hole sparger, and 88-hole scaled ADS sparger tests are carried out to investigate the unstable steam spraying condensation performances. The experimental results indicate that for the multi-hole steam unstable condensation process, the plumes expand and contract in high frequency, and the instantaneous heat transfer coefficients are estimated quantitatively. The multi-hole steam condensation regimes are significantly determined by the steam mass flow flux and water sub-cooling degree, then the double-hole condensation regimes map is proposed based on the key inputting parameters. Moreover, the simplified lumped condensation model for the multi-hole condensation process is developed, in which the upper and lower heat transfer coefficient values limitations are evaluated to be 4.3–5.9 MW/(m2 °C) and 0.89–0.94 MW/(m2 °C), respectively. The ADS 1–3 scaled 88-hole steam condensation results further validate the appropriation of the lumped condensation model, with the heat transfer coefficients estimated as 0.17–2.9 MW/(m2 °C).

Bubble coalescence reduces specific area and weakens the work performance of bubble column. The bubble coalescence near gas sparger which is caused mainly by bubble growing is different from the ones occurring in major liquid. Bubble coalescence efficiency near gas sparger is influenced by many factors including sparger configuration, gas flow rate, bubble deformation, solution composition, etc. This work has conducted a set of visual experiments to study the coalescence characteristics near multi-orifice plate. The experiment parameters cover a wide range of conditions including large scope of gas flow rate, different kinds of solution and orifice configurations. The experimental results suggest that coalescence time is applicable to reflect the influence of the pitch of orifices and gas flow rate on bubble coalescence efficiency. As the number of orifices increases, bubble coalescence efficiency is reduced by the disturbance from the bubbles at adjacent orifices. A hindering coefficient is used to consider the hindering effect of additives on bubble coalescence efficiency. Finally a new calculation expression is established to predict bubble coalescence efficiency near multi-orifice plate whose fundamental form is based on the logistic curve of binary response. The calculated values that refer to this calculation expression are well consistent with the experimental results.