Gas Hold Research Articles

Innovative fluidized bed flotation column for fine particle separation

Flotation columns are extensively utilized to separate fine mineral particles. In highly turbulent environments, the increased collision efficiency between bubbles and particles can lead to improved flotation efficiency of fine particles. The fluidized bed flotation column (FBFC), a new type of flotation equipment, improves the separation efficiency of fine particles by creating a highly turbulent environment in the fluidized zone through the addition of solid particles. This paper investigated the fluidization characteristics, bubble, and gas hold up of the FBFC, along with the flotation efficiency of fine quartz particles. Experimental results showed that introducing gas enhanced the fluidization process in the fluidized bed. The fluidized zone facilitated the fragmentation of bubbles into smaller ones. With increasing liquid velocity, the bubble diameter decreases before subsequently increasing, while the gas holdup initially rises and then declines. The flotation efficiency of fine quartz particles is superior in FBFC with added particles compared to those without added particles. The flotation efficiency of fine particles increases with the rise in both liquid velocity and gas velocity.

Generation of a tripartite photonic state via a double-Λ configuration in a four-level system

Triphotons have a more abundant energy structure compared to biphotons. Furthermore, as the number of photons increases, excellent properties such as entangled multi-qubit states, high security, flexibility, and information capacity are observed. This leads to a growing demand for multi-body quantum information processing. Here, a method is proposed to generate a three-photon entangled state using a single six-wave mixing process in an atomic ensemble. The research examines the temporal correlation characteristics of the triphoton produced in photon coincidence counting measurements, with a focus on the linear and nonlinear susceptibilities of the six-wave mixing process. These properties primarily depend on the fifth-order nonlinear coupling coefficients responsible for the damping Rabi oscillations and the group delay determined by the longitudinal detuning function. To enhance the nonlinear interaction between the optical field and the atomic ensemble, placing the atomic ensemble in a high-quality cavity and utilizing laser cooling techniques to eliminate the internal Doppler broadening effect in the atomic gas hold promise.

Experimental study on resistivity evolution law and precursory signals in the damage process of gas-bearing coal

The occurrence of elevated gas pressure leads to the distortion of the internal pore structure within the coal matrix, thereby exerting a substantial influence on the destabilization of the coal body. This disturbance further contributes to intricate changes in coal resistivity. To delve into the process of gas-induced damage and its implications for coal resistivity, this research employs nuclear magnetic resonance (NMR) technology as a means to characterize coal samples. Moreover, a controlled loading experimental equipment is devised for gas-bearing coal, while concurrently gathering data on resistivity and acoustic emission (AE). The result shows that with increasing applied stress, the change in resistivity within gas-bearing coal exhibits a progressive intensification, manifesting a notable “V”-shaped pattern. This pattern is characterized by an initial rapid decline, succeeded by a subsequent swift increase during the failure stage. The AE signals exhibit a synchronized consistency with the observed resistivity change. With increasing gas pressure, the coal's resistivity exhibits heightened fluctuations, and notably, the range of resistivity at failure under a pressure of 3 MPa is 2.27 times greater compared to that at 0 MPa. Furthermore, the damage variable and constitutive equation for gas-bearing coal based on resistivity is established. The critical value for damage (DE) occurs 1.75 s before the critical value of the resistivity change rate, and 3.88 s earlier than the actual occurrence of damage in the coal body. The correlation between the verified damage and measured stress exceeds 0.8, demonstrating a strong correlation at different stages. The research results contribute to understanding the evolution mechanism of gas instability and hold considerable significance for preventing coal and gas outburst disasters.

Provenance and tectonic settings of the lower Permian siliciclastic rocks in central Inner Mongolia: Implications for the evolution of the Paleo-Asian Ocean

The fine siliciclastic rocks of the Early Permian Shoushangou Formation in West Ujimqin Banner, central Inner Mongolia are a hot spot for Late Paleozoic oil and gas exploration and hold key implications for the tectonic evolution during the closure of the Paleo-Asian Ocean (PAO). Therefore, the sedimentary characteristics of the Shoushangou Formation in West Ujimqin Banner, along with the geochemical and Sm–Nd isotopic characteristics of the clastic rock samples in Well MXD1, were investigated to privde additional constraints on its provenance and tectonic background.The mudstones contain large proportions of quartz, feldspars and igneous debris, and the CIAcorr (0.52–0.66), the A–CN–K plot and the lack of Ce anomalies in REE show a weakly weathered provenance and the chemically unaltered parent rocks, suggestive of the proximal deposition and rapid burial. Slip-roll beddings, gravity flow, Bouma sequences and the (trace) fossil assemblages in the profile indicate that the Shoushangou Formation is mainly a shallow- (semi-)abyssal submarine fan and the lithological information indicates the presence of microfaces including main and lesser water supply channels, interchannels, lobes, natural levees. Furthermore, a narrow continental shelf above the submarine fan and the concentrated zircon age population of the Shoushangou formation suggest that the tectonic background is most likely a retroarc basin.The Al2O3/TiO2 ratio (19–24, average 22), the multivariable principal element source identification diagram and the plots of Th/Sc vs. Zr/Sc and Co/Th vs. La/Sc indicate that the source is mainly felsic, with a minor proportion of intermediate rocks. Trace elemental characteristics (e.g., Th, Zr, Sc, Co, Nd, and REE) deomonstrate that the tectonic setting of the Shoushangou Formation is confined by continental arcs.The whole rock Sm–Nd isotopic spectra of the Carboniferous and Permian strata indicate that the Baolidao arc is the main source of central Inner Mongolia. Additionally, the comparison of the Nd model ages and the zircon U–Pb ages of the Baolidao arc and other entities in the Central Asian Orogenic Belt (CAOB) is in support of a prolonged subduction of the PAO since ∼510 Ma, suggesting that the Baolidao arc was developed from the southern continental arc of the original South Mongolia microcontinent. Accordingly, it is suggested that the Shoushangou Formation was deposited in a retro-arc basin which was strongly influenced by the steep subduction of the PAO and the results collectively suggest that the PAO terminated no earlier than the middle to late Permian.

Foaming and emulsifying properties of saponin glycosides: a natural non-ionic surfactant

Most synthetic surfactants are harmful to humans and can cause health problems after prolonged exposure or consumption. This study explores in extensive detail the use of a natural surfactant saponin, extracted from fruit of S. mukorossi, to synthesise oil in water nanoemulsions and gas–liquid foams. The effects of saponin concentration (0.1–2 wt%), pH conditions (2–10) and salt concentration (100–500 mM) on stability and average droplet diameter of sunflower oil-in-water emulsion were investigated. Emulsions were stable at pH 4–10 and salt concentration 100–400 mM for up to 30 days. Critical micellar concentration of 0.5 wt% and the average hydrodynamic diameter of saponin micelle of 4.25 nm are observed. A gas inducing impeller-based device was used to generate foam from saponin solution having different gas hold up values (εG: 0.31, 0.45 and 0.62). Average bubble size of foam and its stability (drainage rate and half-life) are measured. 100% of saponin solution gets incorporated into foam in every trial. Foam drainage rate increased and half-life decreased with increase in gas holdup. It is shown that saponin can be an effective natural and non-toxic alternative to synthetic surfactants for various industrial applications.

Estimation of the gas hold up and flow regime of a bubble column reactor for the slurry phase hydrocracking of heavy oil

This study investigated gas hold up and flow regimes according to operating conditions (temperature, pressure, superficial gas velocity) for the design of a slurry phase hydrocracking reactor for heavy oil. Heating medium oil, vacuum residue (VR) and hydrocracking products were used in a bubble column reactor which had a diameter of 0.05 m and a height of 2.3 m. The results confirmed that the gas hold up increased and the flow regime transition point was delayed as VR was converted to a hydrocracking product (change in physical properties), and pressure also affected the flow regime transition. Using the dynamic gas disengagement method, the flow regime transition was observed in the actual hydrocracking reaction, and at the same time, it was confirmed that the hydrocracking reaction performance decreased. A VR slurry phase hydrocracking flow regime map is proposed by modifying the existing correlations, and a guide for reactor design and operation is suggested.

Prediction of Fluctuation, Expansion Ratios and Gas Hold Up in a Three Stage Gas-solid Fluidized Bed – A Statistical Approach

Multistage fluidized bed has shown greater performance than the single stage in terms adsorption efficiency, recovery efficiency etc. Thus, experiments have been carried out in a three stage gas-solid fluidized bed. The hydrodynamic characteristicssuch as fluctuation ratio, expansion ratio and gas holdups have been studied. The dependency of these quantities with the system variables like particle size, initial static bed height and superficial gas velocity in each stage of a three-stage fluidized bed have been analyzed. It has been found that both fluctuation and expansion ratios are inverse functions of particle size and static bed height whereas a direct function of superficial gas velocity. However the gas holdup is a direct function of all the three operating parameter.It has also been observed that bed fluctuation and expansion goes on decreasing from lower bed to the upper bed. Further correlations have been developed for all the three stages for fluctuation ratio, expansion ratio and gas holdup using statistical analysis. It has been found that the experimental values of the responses agree well with the values predicted from the models.

Non-invasive monitoring of segregated phases in a biogas plant: An ultrasonic approach

A non-invasive ultrasonic technique (UT) is developed to determine gas-liquid-solid composition inside digester of a biogas plant. The technique involves sweeping a contact type UT probe along the wall of pipes to determine the relative fraction of gas, liquid and solid phases under segregated conditions. The technique is validated at laboratory scale for two-phase (air-water) and three-phase (air-water-solid) systems. The average absolute error in prediction of segregated interfaces is ∼2.5%. Field trials are done on horizontal pipe sections (5 coils) of digester in the plant. More than 50% of the top most pipe run is occupied by gas. For second/third pipe runs solid fraction is around 20–25% while gas fraction is 10–15%. However, for the 4th and 5th pipe rows, the solid fraction is around 40–55%. A gradual increase of gas hold up towards the top regions and larger accumulation of solids at the bottom is expected because of waste feeding at the bottom. The described UT based system represents a novel way forward in use of ultrasound technology to detect segregated multiphase phases in digesters of biogas plants.

Numerical Investigation on a Liquid–Gas Ejector for Carbon Dioxide Removal Using Amine Solution: Hydrodynamics and Mass Transfer Evaluation

The present study investigates the hydrodynamics and mass transfer of the liquid–gas ejector using three-dimensional (air–water) and two-dimensional (CO2/air-MEA (Monoethanolamine) solution) computational fluid dynamics (CFD) modeling. For 3D simulation, validation of the CFD results of this ejector with experimental data (error less than 5%) showed high simulation accuracy. The effects of motive liquid flow rate and outlet pressure parameters on the air entrainment rate and air hold-up are also investigated. It was found that by increasing the outlet pressure by about 70% (from 3587 to 6127 Pag), the rate of gas entrainment and gas hold up decreased by about 37% and 20%, respectively. On the contrary, these parameters showed increasing behavior of about 74% and 15%, respectively, when the mass flow rate of liquid increased by about 21%. In addition, three-dimensional phenomena such as mixing shock and the location of its occurrence are examined, which is the reason for recirculation and vortex in the ejector. Next, by simulating a two-dimensional simulation and changing the inlet fluids to CO2/air-methanol amine, the ejector was designed to simultaneously increase the gas pressure and absorb carbon dioxide. A user-defined function code was used to express the mass transfer from the gas to the liquid phase. The results, in this case, showed that with increasing the outlet pressure of the ejector (from 0 to 2000 Pag), and enhancing the concentration of MEA solution (from 10% to 30%), the CO2 removal boosted from 83% to 95%. A similar behavior was shown when the L/G ratio increased from 3.5 to 5.5. This study serves as a showcase on how to do an exact design and analysis for liquid–gas ejectors in flare gas recovery systems.

Estimation of the Gas Hold Up and Flow Regime of a Bubble Column Reactor for the Slurry Phase Hydrocracking of Heavy Oil

Estimation of the Gas Hold Up and Flow Regime of a Bubble Column Reactor for the Slurry Phase Hydrocracking of Heavy Oil

Towards a CFD-PBE simulation of aerated stirred tanks at high gas hold ups and different flow regimes

In this work we analyze the challenges of the adoption of a population balance approach in aerated stirred tanks operating at high gas volume fractions, in different flow regimes and when segregation of the phases is present, i.e. due to the formation of aerated cavities behind flat blades. A decoupled solution of the equations governing the fluid flow and of the population balance equation (PBE) is adopted to obtain preliminary information on the bubble size distribution and to identify the specific issues that need to be addressed to extend the applicability of the population balance model to different regimes. A workflow is proposed for the simulation of aerated stirred tanks with geometries for which established correlations for the estimation of bubble size are not available and a simplified approach to determine whether a coupled CFD PBE solution may be required is presented.

Effect of Solid Particles on the Gas Hold Up in the Fluidized Bed Columns: Experimental and Mathematical Studies

The present research investigated the effect of solid properties on the gas holdup of the fluidization bed bubble columns (FBCS). All experiments were performed in the constant clear tap water of 80 cm height. The range of solid particle diameters was 0.7 – 2 mm with two different densities of 1075 and 1200 kg/m3, superficial air velocities 4 – 7 cm/s. It was observed that there are proportional relationships between superficial gas velocity and particle diameter with the gas holdup. While an inverse relationship between solid concentration and particle density with the gas holdup. Mathematical and statistical analysis was also used as a powerful way to represent the gas hold up as a function of different operating conditions.

Production and Solubility of Ectoine: Biochemical and Molecular Dynamics Simulation Studies

In this study, ectoine is produced by Streptomyces. sp IBRC-M PTCC 10615. Fermentation parameters such as flow regime, gas hold up, mass transfer coefficient, and mixing time were optimized by statistical analysis. Streptomyces. sp produced a maximal ectoine concentration of 270 mmol/kg at optimal conditions of ectoine and L-aspartic acid. Also, the amount of mass transfer, gas hold up, and mixing time were determined 0,41/s ,0.3, and 40 s, respectively. The amount of ectoine was measured by HPLC. Furthermore, Molecular Dynamics (MD) simulation was used for studying the solubility of ectoine in aqueous media. Equilibrium data such as temperature, potential energy, and volume graphs showed that the solubility of ectoine is 25%more than glycerol. Also, all the achieving graphs from the equilibrium of simulation were confirmed the appropriate structure of the system.

Investigation of the Gas-Liquid Flow in an Agitated Vessel Equipped with an ASI Impeller by Using Tomography Method

In this study, the hydrodynamics of the gas dispersion in an aerated vessel equipped with a newly designed impeller (ASI impeller), a combination of the pitched blade turbine and the Scaba impeller was investigated. The performance of the ASI impeller was compared with the performances of the pitched blade turbine and the Rushton impeller. The non-invasive Electrical Resistance Tomography (ERT) technique was used to assess the gas dispersion inside the mixing vessel. The effects of the volumetric gas flow, and impeller type and speed were investigated on power drawn, gas holdup, and mixing time. An analysis of the experimental data indicated that the ASI impeller exhibited a minimal effect of the gassing on the power drawn compared to the pitch blade and the Rushton turbine. Measured data on gassed power consumption indicated that the ASI impeller was about 45% more efficient than the Rushton turbine and 20% more than the downward PBT under the general operating conditions in bioreactors for gas flow rate about 1 vvm. Also, this impeller showed a higher amount of gas hold up and lower mixing time compared to the two other studied impellers. A dimensionless correlation for the relative power consumption as a function of flow number and Froud number was developed for the aerated agitated tank. Also, a dimensionless correlation was introduced to compute the overall gas hold up as a function of specific power consumption and superficial gas velocity for the gas-liquid agitated system. The overall conclusion from this study demonstrated that the axial-radial ASI impeller is a good energy-efficient impeller for the aeration system and bioreactors based on the results from the investigation of the data in terms of the power consumption, gas holdup, and mixing time.

Simulated oxygen and glucose gradients as a prerequisite for predicting industrial scale performance a priori.

Transferring bioprocesses from lab to industrial scale without loss of performance is key for the successful implementation of novel production approaches. Because mixing and mass transfer is usually hampered in large scale, cells experience heterogeneities eventually causing deteriorated yields, that is, reduced titers, productivities, and sugar-to-product conversions. Accordingly, reliable and easy-to-implement tools for a priori prediction of large-scale performance based on dry and wet-lab tests are heavily needed. This study makes use of computational fluid dynamic simulations of a multiphase multi-impeller stirred tank in pilot scale. So-called lifelines, records of 120,000 Corynebacterium glutamicum cells experiencing fluctuating environmental conditions, were identified and used to properly design wet-lab scale-down (SD) devices. Physical parameters such as power input, gas hold up, , and mixing time showed good agreement with experimental measurements. Analyzing the late fed-batch cultivation revealed that the complex double gradient of glucose and oxygen can be translated into a wet-lab SD setup with only few compartments. Most remarkably, the comparison of different mesh sizes outlined that even the coarsest approach with a mesh density of was sufficient to properly predict physical and biological readouts. Accordingly, the approach offers the potential for the thorough analysis of realistic industrial case scenarios.

Study of Hydrodynamics and Overall Gas Hold Up Validation in Bubble Column by Computational Fluid Dynamics

The study of overall gas hold up has been carried out experimentally with the bed expansion. The superficial gas velocities used for the experiments are 6.369 m/s and 10.616 m/s. The experiment is carried out in a bubble column with inside diameters of 7 cm and a height of 100 cm. Gas from the gas cylinder is supplied through a distributor consisting of a perforated plate and glass beads. The perforated plate has a hole diameter of 1 mm and 0.5 mm. Computational Fluid Dynamic (CFD) using a Eulerian coupled with Population Balance model is developed to predict overall gas hold up and bubble size distribution. The effect of superficial gas velocity, perforated plate diameter, gas properties, and initial liquid level on gas hold up were studied. The use of population balance can significantly improve the overall gas hold-up results compared to constant bubble diameter. It is found that several operating conditions affect the whole gas hold up, namely initial liquid level, superficial gas velocity, and differences in gas properties. While the influence of the difference in perforated plate diameter to overall gas holds up, results are small compared to other operating conditions.

A new approach to measure gas holdup in industrial flotation machines. Part II: Effect of fluid properties

A real-time gas holdup sensor comprising a gas exclusion cell connected to a magnetic flowmeter has been described and tested with water in a previous communication. Gas holdup calculation based on this approach requires, in addition to the measurement of the exit flow velocity provided by the magnetic flowmeter, the sensor’s dimensions and the actual discharge coefficient. This communication characterizes discharge coefficient and gas holdup measurement errors, for one of the original prototypes working with solutions of glycerine and sodium chloride and suspensions of particles having different size distribution and concentration. An underlying fairly unique relationship between discharge coefficient and Reynolds number was found for the fluid tested. This result significantly simplifies the application of the gas hold up sensor at the industrial scale as calibration can be carried out off-line using water instead of the actual slurry without sacrificing accuracy. Gas holdup measurement from the sensor prototype fully immersed in aerated suspensions of different size and concentration were found to be practically unbiased, very precise and insensitive to the fluid properties.

Bubble column photobioreactor for Chlorella pyrenoidosa cultivation and validating gas hold up and volumetric mass transfer coefficient

ABSTRACT The cultivation of microalgae in bubble column photobioreactors is essential to improve the biomass productivity for biofuel production. This work comprises the design and fabrication of bubble column photobioreactor of 20 L culture volume for the cultivation of Chlorella pyrenoidosa. The theoretically parameters such as gas hold up and volumetric mass transfer coefficient was predicted. The bubble column photobioreactor of 20 L culture volume was fabricated. The C. pyrenoidosa was cultivated in bubble column photobioreactor and the actual gas hold up and volumetric mass transfer coefficient was measured and with predicted values. The results showed similar trend of variation of experimental theoretically predicted gas hold up and volumetric mass transfer coefficient at different gas velocities. The comparison of biomass concentration and lipid content of C. pyrenoidosa cultivated in bubble column photobioreactor showed 1.18 ± 0.02 g/ L and 19.04 ± 0.03% dwt, respectively, at the end of the cultivation period as compared with conical flask and glass tank cultivation.

Polyhydroxybutyrate Production from Natural Gas in A Bubble Column Bioreactor: Simulation Using COMSOL.

In this study, the simulation of microorganism ability for the production of poly-β-hydroxybutyrate (PHB) from natural gas (as a carbon source) was carried out. Based on the Taguchi algorithm, the optimum situations for PHB production from natural gas in the columnar bubble reactor with 30 cm length and 1.5 cm diameter at a temperature of 32 °C was evaluated. So, the volume ratio of air to methane of 50:50 was calculated. The simulation was carried out by COMSOL software with two-dimensional symmetric mode. Mass transfer, momentum, density-time, and density-place were investigated. The maximum production of biomass concentration reached was 1.63 g/L, which shows a 10% difference in contrast to the number of experimental results. Furthermore, the consequence of inlet gas rate on concentration and gas hold up was investigated Andres the simulation results were confirmed to experimental results with less than 20% error.

Application of Electrical Resistance Tomography in an Oscillatory Baffled Column for Gas-Liquid Two-Phase Flow

Oscillatory baffled column (OBC) has a high potential for industrial application especially contacting gas and liquid phase. However, there are still lacks of research regarding the dynamics of gas-liquid phase specifically on the visualization of internal flow. Electrical Resistance Tomography (ERT) technique has capabilities to visualize mixing process internally without invading the flow. The objective of this study is to investigate the gas-liquid mixing distribution in an OBC by applying tomography technique model ITS P2000 of ERT system. The parameters investigated are phase distribution, gas hold up and power density. The experimental work was carried out in an OBC with a diameter of 145 mm and 720 mm height. The column is consisted of four planes of sixteen stainless steel ERT electrodes. The results of the research have shown that 70 mm of oscillation amplitude and 2 Hz of oscillation frequency give the best result with 73% of gas hold up and 12433.39W/m3.