Low Gas Flow Rates Research Articles

Remediation of oil-drilling cuttings by ozonation in a bubble flow reactor

Oil-drilling cuttings (ODCs) are the major wastes generated during oil/gas exploration and extraction. In the present work, a new method based on ozonation is suggested for the remediation of ODCs at ambient conditions, without pre-drying. During the ozonation process, the pressure drop across the gas phase along with the pH, redox potential, and temperature of liquid phase are monitored with the aid of built-in sensors. Occasionally, solid and liquid samples are collected to measure the total organic carbon (TOC) of each phase as a function of time, while the concentration of the total petroleum hydrocarbons (TPH) is measured before and after the completion of treatment. The maximum TOC removal efficiency for the solid phase reached ∼60% and that of TPH ∼ 40% whereas the energy efficiency was ∼ 0.1 kWh/g-TOC. The main mechanisms of ODC remediation are the mass-transfer of organic species from the solid to aqueous phase, and the direct oxidation by dissolved ozone, whereas their synergistic action is reflected in fluctuations of TOC concentration in liquid phase. The TOC removal efficiency of the solid phase increases with the flow rate decreasing, the ozone concentration increasing, and the mass ratio of ODC to seawater (SW) increasing. Ozonation in the liquid phase after its separation from treated ODC proceeds very fast through the direct oxidation by ozone. The process energy efficiency is favoured for low ozone concentration, low gas flow rate, high ODC to SW mass ratio, oxygen as feed gas, and without the addition of sodium dodecyl sulphate (SDS) as surfactant.

Computational Fluid Dynamics Modeling of Solar Thermal Dry Reforming of Methane in a Parabolic Trough

Computational fluid dynamics simulations of solar-thermal dry reforming of methane using a parabolic trough configuration were performed. Parametric simulations of different combinations of gas flow rate, receiver tube emissivity, and geometric concentration ratio were conducted to determine configurations that could achieve the required catalyst temperatures of at least 700 °C to achieve high conversion of CH4 and CO2 to H2 and CO. Results showed that the concentration ratio of the parabolic trough collector had to be increased from ~70 to ~120 and the receiver-tube emissivity had to be reduced to ~0.2 to achieve bulk average catalyst temperatures of greater than 700 °C. Lower gas flow rates also reduced enthalpic heat losses and increased catalyst temperatures.

Insight into the formation of slag eyes and the mechanism of slag entrapment in the steel-ladle refining process: Hydraulic modeling and numerical simulations

Slag eyes are the upper exposed areas of molten steel in a refining ladle that are formed due to excessive bottom argon bubbling. This phenomenon frequently occurs in the steel-refining process and can lead to slag entrapment and re-oxidation of molten steel. Taking a 150-t industrial steel ladle as the research object, the effects of a dual-plug gas-blown process on the slag-eye size were studied using hydraulic modeling and large-eddy simulations. The experimental results showed that at higher gas flow rates such as 9.1 and 11.7 normal liters/min (Nl/min), the relative central angle of the two porous plugs had a significant effect on the slag-eye size; conversely, at lower gas flow rates, its influence could be ignored. Due to the tendency of the two small slag eyes to merge, the 0.6R–45° (R being the bottom radius of the ladle) case resulted in a larger total slag-eye area compared to the cases with other angles. The 0.6R–135° case showed the most beneficial results for reducing the slag-eye size. Additionally, the numerical simulations helped us to visualize the bubble-uplifting and slag-eye formation processes, and they allowed an exploration of the slag-entrapment mechanism. The simulation results showed that the symmetric gas-blown mode can reduce slag entrapment when compared with the asymmetric mode for the 135°–11.7 Nl/min case; this will be favorable to control the cleanliness of the molten steel. Additionally, analysis of both liquid-level fluctuations and turbulent-kinetic-energy distributions further confirmed the advantages of the symmetric gas-blown mode for suppressing slag entrapment.

An experimental investigation into the effect two-phase flow induced vibrations have on a J-shaped flexible pipe

Multiphase flow inside of pipes occurs in a wide variety of engineering applications, including offshore deep-water oil and gas transport. Vibrations induced by the flow inside of the pipe can lead to its mechanical failure and thus lead to uncontrolled release of the fluids being transported. In subsea applications, flexible J-risers are often employed to deliver the produced fluids from the seafloor to the host platform. Despite the potentially significant liabilities associated with subsea hydrocarbon leaks, there has been a distinct lack of investigations into how flow induced vibrations in large scale, pressurised flexible J-risers can lead to system integrity loss. Previous investigations have generally focused on the response of rigid pipes or small scale, unpressurised flexible risers. This study presents an investigation into the response of a 10 m long, 50.8 mm internal diameter composite riser containing a tensile armour helical structure to a variety of two-phase, water-nitrogen flows at 10.8 barg of pressure and ambient temperature. High speed cameras were used to investigate the structure of the flow at either end of the flexible riser, whilst synchronised surface mounted strain gauges and accelerometers were used to investigate the response of the pipe. Time-averaged data were acquired to assess the general response of the pipe, whilst a statistical analysis of the fluctuations highlighted the movement of the pipe. One-dimensional and computational fluid dynamics simulations were used to define the experimental test matrix and provide further insight into the structure of the flow inside the J-riser. Single-phase gas flow was found not to cause the J-riser to move significantly, whilst multiphase flow led to significant in-plane movement of the pipe. Increasing the liquid flow rate (or decreasing the gas flow rate) increased the mean strain experienced by the pipe. At low gas flow rates, the pipe oscillated smoothly about its mean position, but at higher gas flow rates a violent intermittent whipping motion was observed. The latter produced large in-plane and out-of-plane movement of the pipe which could pose a threat to system integrity. This work offers new insights into fluid-structure interactions in large scale engineering applications, contributing to improved system design and control.

Influence of atmospheric plasma spraying process parameters on microstructure and properties of yttrium oxide coatings

Y2O3 coatings were fabricated on using atmospheric plasma spraying (APS). The effects of different process parameters on the microstructure and properties of the coating were analyzed. The results show that the overall morphology of Y2O3 coatings are smooth at high spraying power, low spraying distance and low primary gas flow rate, which is consistent with the change trend of porosity and hardness. The minimum porosity of coating is about 1.4%. The roughness of coatings isn’t sensitive to changes in parameters. Y2O3 coatings have excellent corrosion resistance. The smaller the porosity of Y2O3 coating, the better the corrosion resistance.

Intranasal Vaccine Formulation: Advancing Towards Nasal Dry Powder Formulation

Unlike conventional mRNA vaccines,intranasal vaccines display several advantages, including the ability to generatestrong mucosal immunity. However,the formulation challenges associated with intranasal mRNA vaccines have so farhindered their extensive application and further research in the area of formulationdevelopment and optimisation are required before translation. This study aimsto optimise the manufacturing conditions of inhalable dry powders by examining theimpact of temperature and lipid composition on liposome particle size and theeffect of spray-drying parameters on the particle size of spray-dried powders. The results indicate that liposomesgenerated at 20°C exhibited notably larger sizes than those produced at 55°C,irrespective of the lipid composition. Notably, dry powder formulations featuringlarger particle sizes were achieved at a low gas flow rate of 25mm.

Influence of ionization volume and sample gas flow rate on separation power in gas chromatography-ion mobility spectrometry

In this work, the influence of the sample gas flow rate and the ionization region volume of an ion mobility spectrometer (IMS) used as a detector in gas chromatography (GC) on GC-IMS peak shape has been investigated. Therefore, a drift tube IMS with a field-switching ion shutter, a defined ionization region volume and an ultra-violet radiation source was used. To identify the influence of the sample gas flow rate entering the ionization region (equals the GC carrier gas flow rate if no further make-up gas is used) and the ionization region volume on peak broadening and signal intensity, different sample volumes as they would elute from a GC were tested at a variety of sample gas flow rates at a given ionization region volume. The results clearly show that for low sample gas flow rates a depletion of sample molecules in the ionization region leads to a significant decrease in effective detector volume but also to reduced signal intensities. Therefore, for optimal performance of a GC-IMS, the optimal operating point of the GC should match the flow range, where the IMS provides the best compromise between signal-to-noise ratio and peak broadening.

Characterization of CNC Nanoparticles Prepared via Ultrasonic-Assisted Spray Drying and Their Application in Composite Films.

The ultrasonic-assisted spray dryer, also known as a nano spray dryer and predominantly used on a lab scale in the pharmaceutical and food industries, enables the production of nanometer-sized particles. In this study, the nano spray dryer was applied to cellulosic materials, such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). CNC suspensions were successfully dried, while the CNF suspensions could not be dried, attributable to their longer fibril lengths. The nano spray drying process was performed under different drying conditions, including nebulizer hole sizes, solid concentrations, and gas flow rates. It was confirmed that the individual particle size of nano spray-dried CNCs (nano SDCNCs) decreased as the nebulizer hole sizes and solid contents of the suspensions decreased. The production rate of the nano spray dryer increased with higher solid contents and lower gas flow rates. The resulting nano SDCNCs were added to a polyvinyl alcohol (PVA) matrix as a reinforcing material to evaluate their reinforcement behavior in a plastic matrix using solvent casting. After incorporating the 20 wt.% nano SDCNCs into the PVA matrix, the tensile strength and tensile modulus elasticity of the neat PVA nanocomposite film increased by 22% and 32%, respectively, while preserving the transparency of the films.

Nitrogen fixation as NOx using air plasma coupled with heterogeneous catalysis at atmospheric pressure

AbstractThis study presents insights into the use of activated catalysts to improve the energy efficiency of production in atmospheric pressure air plasma. The introduction of catalysts in the direct current glow discharge system reduces the energy cost of production by up to 45% at low gas flow rates. Notably, even when positioned away from the plasma zone, the catalyst enhanced production, suggesting a significant role for the catalytic activation of downstream neutral species. The study also introduced a novel approach involving an air plasma jet infused with floating catalyst powder. This method significantly increased energy efficiency at higher discharge currents, with an associated energy cost of 2.9 MJ/mol for production.

Laser Pyrolysis of Iron Oxide Nanoparticles and the Influence of Laser Power.

The purpose of this study was to investigate the synthesis of iron oxide nanoparticles under two different conditions, namely high and low gas flow rates, using laser pyrolysis and to examine the influence of laser power. The attained nanoparticles have been characterised regarding their stability and hydrodynamic dimensions by dispersive light scattering analysis (DLS), structure-X-ray diffraction (XRD), elemental composition-energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), and morpho-structural characterisation achieved by transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). For a better understanding of the laser power influence, the residence time was also calculated.

Modelling Hydrate Deposition in Gas-Dominant Subsea Pipelines in Operating and Shutdown Scenarios

This study addresses a significant research gap related to hydrate formation in subsea gas pipelines, with a specific focus on deposition rates during shutdown scenarios, which has received limited attention in previous studies. Past research has employed various methodologies, including experimental, analytical, and computational fluid dynamics (CFD) approaches, to predict hydrate formation conditions, but none have tackled the prediction of hydrate deposition during shutdowns. In this study, we employ a multiple linear regression modeling approach using the MATLAB regression learner app. Four distinct regression models were developed using data generated from 81 CFD simulations, utilising a 10 m length by 0.0204 m diameter 3D horizontal pipe model in Ansys Fluent, as previously developed Through cross-validation against experimental data, the standard linear regression model emerged as the most reliable choice for predicting hydrate deposition rates, providing predictions within ±10% uncertainty bounds of experimental results up to pressures of 8.8 MPa at hydrate-forming temperatures. The uniqueness of this new model lies in its ability to estimate the risk of hydrate deposition in subsea gas pipelines, especially with low gas flow rates and during shutdown periods, which are critical for maintenance planning. Furthermore, by estimating depositional volumes, the model predicts hydrate slurry volumes at receiving facilities, contributing to energy sustainability and benefiting gas transport pipeline operators, particularly in aging gas fields with declining production.

Self-mode transition, oscillation and inverse hysteresis in ECR discharges

Positive and negative feedback of microwave (MW) ECR (electron cyclotron resonance) discharges in cross magnetic field were manipulated by a three-stub coaxial tuner. Unstable ECR discharges in the positive feedback region, such as the self-mode transition between the ordinary (O)-wave mode and extraordinary (X) one, inverse hysteresis, and oscillation, were investigated using a time-resolved MW power meter, high speed camera, and thermocouple. In the positive feedback region, the self-O → X wave mode discharge transition can be driven under the “hot” wall condition, while the counterpart, namely the self-X → O wave mode transition, is observable for the “cold” wall; the inverse hysteresis and oscillation take place at low and moderate gas flow rates, respectively. The mechanism underlying the self-mode transitions and instabilities is the discharge shift due to the gas heating effect. For MW ECR discharges to become stable, as indicated in previous experiments, they should be mismatched in the negative feedback region.

CPFD simulation of an electrically heated fluidized bed calciner with binary particles

Electrifying a calciner with clean energy can cut fuel emissions and produce a stream of relatively pure CO2 from the calcination reaction (CaCO3 → CaO + CO2), which can be utilized or stored. A fluidized bed calciner offers a high heat transfer coefficient and requires low gas flow rates for operation. The design of such a reactor is studied in this work. It is not possible to fluidize raw meal directly, so a binary mixture of coarse lime particles and fine raw meal is used. The commercial Barracuda CPFD software is applied. The model was first validated against experimental results and then used to find an optimized design. The results indicate that the suggested pilot-scale fluidized bed calciner can operate between 10 and 16 t/h of raw meal feeding with a calcination degree above 90% and with negligible coarse particle entrainment. The calciner needs 0.05–0.09 kg-CO2/kg-raw-meal for the operation, so the required gas recycling is low. Overall the calciner operation is smooth, and such a design could be used for electrification combined with CCUS.

Experimental study of swirling flow pneumatic liquid-carrying characteristics in the vortex tool inserted tube under liquid loading conditions

Liquid unloading by vortex tool is one of the most important applications of swirling flow pneumatic conveying. However, due to swirl decay, the evolution of gas–liquid flow patterns and the dynamic characteristics of pressure drop downstream of the vortex tool are much more complex than those in non-swirling flow. In this study, the gas–liquid flow patterns and pressure drop inside the vortex tool inserted tube (ID = 60 mm) under liquid loading conditions were experimentally studied and compared with those of the plain tube. With the superficial gas velocities ranging from 0.5 to 6.0 m/s and superficial liquid velocities of 0.01, 0.02, and 0.04 m/s, the effects of the structural parameters and stages of vortex tools on the pressure drop were discussed. The experimental results reveal that three distinct swirling flow patterns can be identified downstream of the vortex tool, namely swirling gas column flow, swirling churn flow and swirling annular flow. The insertion of vortex tool facilitates an earlier transition of the churn flow to the annular flow, and the induced swirling flow can restrain the liquid from falling back. The helix angle of the corkscrew deflector has a more significant effect on the pressure drop than its length. By reducing the helix angle from 54° to 45°, the total pressure drop and downstream pressure gradient are significantly decreased, even lower than those of the plain tube. But the series combination of 54° and 45° vortex tools results in a significant increase in the downstream pressure gradient. Additionally, at low gas flow rate, negative frictional pressure drop occurs in both plain tube and vortex tool inserted tube. Hence, the new friction factor correlations were established respectively for the positive and negative friction regions in the cases of the tube with and without vortex tool, and most of the frictional pressure gradient predictions are within an error band less than 20%.

Suppression of humping bead defects in high-speed triple-wire gas indirect arc welding through compensation gas

Triple-wire gas indirect arc welding (TW-GIA) has significant advantages of high deposition rate and low heat input. However, the humping bead defects in high-speed TW-GIA welding limits the improvement of welding speed. In this article, the feasibility of compensation gas to suppress the humping bead in TW-GIA was explored, and the influence on molten pool flow and arc stability was revealed. The results show that the compensation gas with jet angle of 90 °has the ability to suppress the humping bead and reduces the oxygen content of the weld. When the compensation gas flow rate is less than 30 L/min, the decrease of arc pressure leads to the decrease of reverse flow velocity of liquid metal. And the vertical downward impact force caused by compensation gas can directly inhibit the uplift of the liquid metal, which is beneficial to suppress the humping bead. In addition, the compensation gas carry in high ionization energy gas, which reduces the welding current and increases the range of conductive channel. The low gas flow rate with the jet angle of 90° has little effect on the arc stability, but the flow rate exceeding 30 L/min significantly increases the degree of arc disorder.

Balanced multiphase mixing through a narrow gap

Mixing of a two-phase flow through a gap connecting adjacent channels was investigated for a variety flow rates and two gap heights. The mixing was characterized by the amount of gross liquid and net gas mass transfer from one channel to the other. The liquid mixing through the gap was calculated based on the measured mass flow rates and dye tracer concentrations at the inlet and outlet of each channel. The gas net transfer, phase fraction distributions, bubble size distributions, and gas interface velocity were measured using dual-plane wire mesh conductivity sensors at both inlets and outlets. Additionally, imaging of the fluorescent tracer dye and air bubbles were used together with Spectral Proper Orthogonal Decomposition (SPOD) to further characterize the mixing mechanisms. The water inlet Reynolds number was varied from 4 to 10×104 and the volumetric gas quality from 0 to 0.35 which resulted in gas volume fractions up to 15%. All conditions were in the bubbly flow regime. Air was introduced by a needle array producing nominally monodispersed bubbles at lower gas flow rates with broader bubble size distributions at higher gas flow rates. The Sauter mean diameter varied from 3 to 8 mm, depending on flow rates. For these balanced flows large coherent structures dominated the mixing. However, even mere O(5%) volumetric quality gas injection could significantly suppress the coherent structures reducing mixing by over 50%.

Plasma-catalytic CO2 methanation over NiFen/(Mg, Al)Ox catalysts: Catalyst development and process optimisation

Plasma-assisted catalytic carbon dioxide (CO2) methanation is a promising approach to valorise CO2 under mild conditions, and the system requires rational design regarding both catalysts and processes to advance it towards practical applications. Herein, the bimetallic NiFen/(Mg, Al)Ox catalysts were developed for plasma-catalytic CO2 methanation, and the effect of atomic ratio of Ni and Fe and reduction temperature on the catalysts was investigated systematically. The findings show that a higher reduction temperature was beneficial to the formation of Ni3Fe alloy and abundant surface oxygen vacancies, and increased CO2 adsorption ability. As a result, the NiFe0.1/(Mg, Al)Ox-800 catalyst led to a good catalytic performance in the plasma-assisted catalysis with about 84.7% CO2 conversion and 100% methane (CH4) selectivity. In addition, this study also employed response surface methodology (RSM) to explore the optimisation of plasma-catalytic CO2 methanation for the first time. Results from RSM show that in the plasma-catalytic system the selective CO2 hydrogenation to CH4 was favoured by higher applied voltage, lower gas flow rate and higher gas ratio (H2: CO2).

Numerical and experimental investigation of gas flow field variations in three-dimensional printed gas-dynamic virtual nozzles

Gas-dynamic virtual nozzles (GDVNs) play a vital role in delivering biomolecular samples during diffraction measurements at X-ray free-electron laser facilities. Recently, submicrometer resolution capabilities of two-photon polymerization 3D printing techniques opened the possibility to quickly fabricate gas-dynamic virtual nozzles with practically any geometry. In our previous work, we exploited this capability to print asymmetric gas-dynamic virtual nozzles that outperformed conventional symmetric designs, which naturally leads to the question of how to identify the optimal gas-dynamic virtual nozzle geometry. In this work, we develop a 3D computational fluid dynamics pipeline to investigate how the characteristics of microjets are affected by gas-dynamic virtual nozzle geometry, which will allow for further geometry optimizations and explorations. We used open-source software (OpenFOAM) and an efficient geometric volume-of-fluid method (isoAdvector) to affordably and accurately predict jet properties for different nozzle geometries. Computational resources were minimized by utilizing adaptive mesh refinement. The numerical simulation results showed acceptable agreement with the experimental data, with a relative error of about 10% for our test cases that compared bell- and cone-shaped sheath-gas cavities. In these test cases, we used a relatively low sheath gas flow rate (6 mg/min), but future work including the implementation of compressible flows will enable the investigation of higher flow rates and the study of asymmetric drip-to-jet transitions.

Influence of aqueous foam on gas–liquid flow development of hilly-terrain wet gas pipeline with surfactant injection

This study presents surfactant injection as a replacement technology for mechanical pigging to reduce liquid accumulation for wet gas transmission. The hilly terrain gas/liquid flow development characteristics under surfactant injection were explored in pipelines, and a comprehensive experiment was performed through flow observation and the measurement and analysis of the flow characteristic parameters. The 250 ppm sodium dodecyl sulfate (SDS) surfactant was employed according to the variation characteristics of the flow pattern and pressure drop at different concentrations. Flow observations and liquid holdup characteristics indicate that owing to the formation of aqueous foam, the gas/liquid interface and phase characteristics change significantly, and the liquid holdup decreases by several or even more than ten times and maintains a low value (0.004–0.070), except for the initial gas–liquid flow at low gas flow and high liquid flow rates. The aqueous foam effectively suppresses the slug and pseudo slug initiation, the gas/liquid convection of the slug body, and the large wave rolling of the pseudo-slug body, which induces the dissipation of intermittent flow. The pressure drop under the influence of aqueous foam decreases drastically (60% ∼ 85%) at certain gas and liquid velocities and fluctuates smoothly near zero over a wide experimental range. The surfactant suppression on partially blocked pseudo-slug body induces a significant decrease of pseudo-slug frequency from 0.17 ∼ 0.42 Hz to 0 ∼ 0.06 Hz and transitional velocity from 1.21 ∼ 1.90 m/s to 0 ∼ 1.11 m/s. This research is highly significant for surfactant injection schemes and efficient and sustainable production.

Characterizing a nitrogen microwave inductively coupled atmospheric-pressure plasma ion source for element mass spectrometry.

A high-power nitrogen-based microwave inductively coupled atmospheric-pressure plasma was coupled to a quadrupole mass spectrometer to investigate its characteristics as an ion source for element mass spectrometry. The influence of operating conditions on analyte sensitivity, plasma background, and polyatomic ion formation was investigated for conventional solution-based analysis. By varying the forward power and the nebulizer gas flow rate, the plasma background ions were found to decrease with increasing gas flow rates and decreasing operating power. Analyte ions showed different trends, which could be related to the physical-chemical properties of the elements. We could identify three groups based on the location of maximum intensity in the power vs. flow rate contour plot. Atomic ions of elements with low first ionization energy and low oxygen bond strength were found to maximize at a high nebulizer gas flow rate and lower microwave power. Elements with intermediate ionization energy and higher oxygen bond strength required higher power settings for optimum sensitivity, while elements with the highest ionization energies required the highest power and lowest gas flow rates for their optimization. The latter group showed a substantial suppression in sensitivity compared to elements of similar mass, which is considered to result from the high abundance of NO in the plasma source, whose ionization energy is close to that of these elements. Metal oxide ions were found at similar or higher abundances than in the conventional argon-based ICP and could be minimized only by using a low gas flow rate and high power settings. These general trends were also observed when the vacuum interface was modified. To change the dynamics of the supersonic expansion, different sampler cone orifice sizes and sampler-skimmer distances were investigated and the interface pressure was lowered through an additional pump. These modifications did not yield significant differences in ion transmission but lowering the interface pressure reduced the relative abundance of metal oxide ions. The limits of detection were evaluated for optimized plasma conditions and found comparable to those of an argon ICP source with the same mass spectrometer.