Evaluation of gas-liquid separation performance of natural gas filters

Fibrous filters are often used to remove contaminants including both dusts and liquid droplets from natural gas. This paper aims to evaluate the gas-liquid separation performance of three types of cartridge filters used in the West-East natural gas transmission project. The comparison of the original pressure drop of clean filters and the evolution of pressure drop as liquid droplets deposited in the filter media are described. The original pressure drops of these filters were similar but the pressure drops at a steady state were different. Fractional efficiency was used to study the separation performance of cartridge filters. Droplets at the outlet of the filters had small diameters, no more than 3 μm, but were very numerous. The effect of filtration velocity on gas-liquid separation performance was analyzed. Higher filtration velocity indicated better gas-liquid separation performance. Finally the quality factor related to pressure drop and filtration efficiency was applied to evaluate the gas-liquid separation performance.

FLUID DYNAMICS IN A GAS-STIRRED LADLE——A Separated Flow Model with Stochastical Trajectories

A separated flow model with stochastical trajectories has been developed to describe the fluid flow in a bubble stirred ladle.The bubble dispersion,turbulent characteristics and gas-liquid interactions can be predicted by this mathematical model.The bubble flow as a dispersed phase is treated in a Lagrangian frame of reference and the analysis of the turbulent flow for liquid phase is conducted in a Eulerian field.The interactions between bubbles and liquid phases are considered as a bubble source term in the control equation for a continuous phase. The Monte Carlo sampling method is used to determine the bubble trajectories.The homoge- neous flow model is also taken into consideration so that it can be compared with the sepa- rated flow model.Numerical predictions using a water model of a ladle show that the pre- dicted results of the separated flow model agree satisfactorily with the experimental results, but the prediction of the homogeneous flow model are not in good agreement with the experi- mental results.

Experimental investigation on separation characteristics of axial cyclone separator

Axial cyclone separator has been widely applied in chemical production as an efficient gas-liquid separation device.In this study,a new axial cyclone separator with integrated swirler and exhaust pipe is designed to achieve the development goal of compact structure for advanced engine,and the distribution characteristics of swirling flow patterns as well as the variation in separation characteristics are investigated under slug flow pattern.Based on flow visualizations and fluctuation characteristics of pressure signals,three typical flow patterns,namely,slug flow,swirling intermittent flow,and swirling annular flow,in the horizontal swirling separation flow are characterized.It is investigated how the inlet conditions affect the separation characteristic parameters.The separation purity and extreme points of the air separation efficiency are independent of the inlet liquid flow rate.The separation pressure drop is quadratically related to the inlet air flow rate.Based on the drift-flux model and other methods,the prediction methods for the air separation efficiency and pressure drop are proposed,and the prediction accuracy is within±20%,which may provide instructions for the practical application of axial cyclone separator.

Surface nanobubble characterization and its enhancement mechanisms for fine-particle flotation:A review

Froth flotation is often used for fine-particle separation,but its process efficiency rapidly decreases with decreasing particle size.The efficient separation of ultrafine particles(UFPs)has been a major challenge in the mineral processing field for many years.In recent years,the use of surface nanobubbles in the flotation process has been recognized as an effective approach for enhancing the recovery of UFPs.Compared with traditional macrobubbles,nanobubbles possess unique surface and bulk characteristics,and their effects on the UFP flotation behavior have been a topic of intensive research.This review article is focused on the studies on various unique characteristics of nanobubbles and their mechanisms of enhancing the UFP flotation.The purpose of this article is to summarize the major achievements on the two topics and pinpoint future research needs for a better understanding of the fundamentals of surface nanobubble flotation and developing more feasible and efficient processes for fine and UFPs.

Characteristics of flow and liquid distribution in a gas-liquid vortex separator with multi spiral arms

Fischer-Tropsch(F-T)synthesis is an important route to achieve the clean fuel production.The perfor-mance of gas-liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F-T process.In order to remove the bottleneck,a gas-liquid vortex separator with simple structure,low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period.The RSM(Reynolds Stress Model)and DPM(Discrete Phase Method)are employed to simulate the flow characteristics and liquid distribution in the separator.The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone.The transverse vortex at the top of spiral arm entrains the droplets with small diam-eter into the upper annular zone.The entrained droplets rotate upward at an angle of about 37.4°.The screw pitch between neighbor liquid threads is about 0.3 m.There is a top liquid ring in the top of annular zone,where the higher is the liquid phase concentration,the lower is the separation efficiency.It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity.The screw pitch is not affected by both inlet velocity and annular zone height.The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height.The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity.When the height of annular zone is more than 940 mm,the separation efficiency is not changed.Therefore,the annular zone height of 940 mm is thought to be the most economical design.

Performance Prediction of the Helico-axial Multiphase Pump

A modified one-dimensional model is developed for prediction of multiphase pump performance. Taken into account in the model are the gas compressibility, the slip speed gap between two phases and the flow cross-sectional depth gradient in the flow line. By using this model, we can select appropriate geometrical parameters of the impellers and guide vanes, and thus higher-pressure boost is obtained but phase separation does not occur. Accordingly, the design method can be optimized. The drag coefficients are analyzed for different flows. Results predicted by the modified model are compared with a series of experimental data and found in good agreement. This model provides a convenient and economical tool for engineering design over a traditional one.

Gas-liquid flow splitting in T-junction with inclined lateral arm

This paper studies the gas-liquid flow splitting in T-junction with inclined lateral arm. The separation mechanism of the T-junction is related to the pressure distribution in the T-junction. It is shown that the separation efficiency strongly depends on the inclination angle, when the angle ranges from 0° to 30°, while not so strongly for angles in the range from 30° to 90°. Increasing the number of connecting tubes is helpful for the gas-liquid separation, and under the present test conditions, with four connecting tubes,a good separation performance can be achieved. Accordingly, a multi-tube Y-junction separator with four connecting tubes is designed for the experimental investigation. A good agreement between the simulated and measured data shows that there is an optimal split ratio to achieve the best performance for the multi-tube Y-junction separator.

Investigation of Self-Priming Process of a Centrifugal Pump with Double Blades

The gas-liquid two-phase flow patterns of a centrifugal pump during the self-priming process were investigated numerically and experimentally.The Euler-Euler multiphase model and SST k-ω turbulence model were applied for simulating the self-priming process.Meanwhile,the changes of motor speed and self-priming height were considered in the simulation.The overall transient two-phase flow features and water level distributions were mapped.Results showed that the self-priming process was divided into three stages.The liquid level in inlet-pipe rose in oscillation during self-priming process.The variations of water level during self-priming process of numerical simulation and test result agreed well.The inlet-pipe(Ver)was filled at 22 s and 24 s respectively numerically and experimentally.The bubble cloud circulated in the volute during middle stage of self-priming process,and breakup into smaller bubbles by shear force and tongue,and then discharged into chamber.The bubbles in the outlet-pipe mainly included bubbly flow and slug flow at the last stage of self-priming process,which is morphologically consistent with the test results.Also,during the self-priming process,the reflux liquid was pressed by blades and fully mixed with gas;that is the way to realizing the function of self-priming.

FTIR investigation of the interfacial properties and mechanisms of CO_(2) sorption in porous ionic liquids

Porous liquids,which are liquids with permanent porosity,have received significant attention as a new class of materials with the potential for far-reaching impacts in a variety of applications including gas separation.In this work,in situ Fourier transform infrared spectroscopy measurements were conducted to investigate the mechanism of carbon dioxide absorption in a porous ionic liquid consisting of ZIF-8 combined with 8,80-(3,6-dioxaoctane-1,8-diyl)bis(1,8-diazabicyclo[5.4.0]undec-7-en-8-ium)bis(trifluoromethanesulfonyl)imide([DBU-PEG][(Tf_(2)N)_(2)]).While the vibrational modes of the pure ionic liquid remain relatively unchanged,the incorporation of carbon dioxide leads to slight structural fluctuations in the ZIF-8 framework whether it is pure solid or as integrated into the porous ionic liquid.The analysis of the vibrational modes of the porous ionic liquid suggests that the interaction of the CO_(2) occurs more strongly with the ring structure of the ZIF-8 framework.The splitting of the asymmetric stretch of the CO_(2) into multiple peaks upon sorption indicate the presence of multiple environments,which could be a combination of free and physisorbed CO_(2) or simply multiple binding sites within the porous ionic liquid.A better understanding of gas sorption mechanisms in this unique material could lead to new porous ionic liquids with enhanced separations properties.