Gas-liquid Layer Research Articles

VORTEXGAS-LIQUIDSEPARATOR

Results of a research of the vortex contact device of the tangential type intended for separation of drops and cleaning of industrial emissions of gaseous inclusions in rectifying and absorbing columns, hydrolysis devices, dryers, evaporators, scrubbers, gas-liquid reactors are presented. In which removal of disperse particles from a stream and absorption of components of gas is carried out directly in the rotating gas-liquid layer of absorbent in the field of the greatest influence of forces of inertia and a high-speed pressure of gas. What allows to reach the high speed of the movement of a gas stream and to provide catching of drops up to 0.4 kg on one kilogram of air. In work, two types of zavikhritel are investigated and the main modes of interaction of gas with liquid bubbling and ring are revealed. The size of coefficient of hydraulic resistance of the contact device was equal 0.8–1.1, and a share of a bryzgounos – less than 0.01. It is established that at an expense of drops in a gas stream up to 0.01 kg/s, the size of coefficient of resistance has increased by 1.25 times. Values of superficial coefficient of a massootdacha at gas absorption by liquid are reached equal to 0.9·10-3 m/c., and the interphase surface has made equal 0.1–0.9·10-3 m/c.Advantage of the specified device is his steady and effective work in the wide range of loadings on gas, liquid, rather low hydraulic resistance, and small metal consumption. Dependences for determination of gas content, angular and linear speed, height of the rotating layer of liquid and size of coefficients of a massootdacha allowing to carry out calculation of industrial samples of the corresponding equipment are presented.

PROBLEMS AND PROSPECTS OF PRODUCTION AND QUALIFICATION OF PHOSPHORIC ACID

The qualification of phosphoric acid is carried out depending on the use of phosphates of various deposits and the necessary quality of the final products. An acquisition of phosphoric acid of the required quality should be carried out taking into account three aspects: resource-energy, ecology and complex processing. Solving the problems of one aspect entails solving the problems of the other aspects. The rational use of natural resources and the reduction of environmental pollution is the determining factor in the choice of technological regimes for complex processing of raw materials with a reduction in the volume of waste of all kinds or transferring them into forms easily recyclable or specially stored. The absence of economically sound technologies for processing phosphogypsum determines its preferential warehousing. The second component that requires recycling is fluorine. In this regard, the purification of phosphoric acid from fluorine should use technologies that realize the trapping of fluorine compounds released into the gas phase. This is relevant from the point of view of the complexity of processing raw materials with the extraction of rare-earth elements. The use of mechanochemical activation makes it possible to achieve a nanoscale level. To a lesser extent, this aspect relates to the stage of sulfuric acid decomposition, proceeding with the participation of three phases: solid, liquid and gas. In turn, the surface structure of the gas-liquid layer plays the role of an energy barrier for evaporation. To establish the basic energy patterns of concentration and defluorination n the disc apparatus and to optimize the process, a thermophysical model was developed in which the range of effective parameters was determined by the joint solution of a number of equations for the desired ingredients in the phosphoric acid concentration range of 52-65%. The solution of the problem of complex purification of wet-process phosphoric acid can be carried out by adsorption methods that allow to remove to some extent almost all impurities.For citation:Smirnov N.N., Smirnova D.N., Ilyin A.P., Kochetkov S.P. Problems and prospects of production and qualification of phosphoric acid. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 48-56.

Characterization of horizontal air–water two-phase flow

This paper presents experimental studies performed to characterize horizontal air–water two-phase flow in a round pipe with an inner diameter of 3.81cm. A detailed flow visualization study is performed using a high-speed video camera in a wide range of two-phase flow conditions to verify previous flow regime maps. Two-phase flows are classified into bubbly, plug, slug, stratified, stratified-wavy, and annular flow regimes. While the transition boundaries identified in the present study compare well with the existing ones (Mandhane et al., 1974) in general, some discrepancies are observed for bubbly-to-plug/slug, and plug-to-slug transition boundaries. Based on the new transition boundaries, three additional test conditions are determined in horizontal bubbly flow to extend the database by Talley et al. (2015a). Various local two-phase flow parameters including void fraction, interfacial area concentration, bubble velocity, and bubble Sauter mean diameter are obtained. The effects of increasing gas flow rate on void fraction, bubble Sauter mean diameter, and bubble velocity are discussed. Bubbles begin to coalesce near the gas–liquid layer instead of in the highly packed region when gas flow rate increases. Using all the current experimental data, two-phase frictional pressure loss analysis is performed using the Lockhart–Martinelli method. It is found that the coefficient C=24 yields the best agreement with the data with the minimum average difference. Moreover, drift flux analysis is performed to predict void-weighted area-averaged bubble velocity and area-averaged void fraction. Based on the current database, functional relations for ≪vg≫ vs. <j> and <α> vs. <jg>/<j> have been studied. It is found that ≪vg≫ – <j> method predicts the void-weighted area-averaged bubble velocity and area-averaged void fraction better compared to <α> – <jg>/<j> method.

Calculation of pressure drop of dual-flow plates in the regime of mobile gas-liquid layer

As a result of the processing the experimental data to determine the pressure drop of dual-flow plates, criteria equations were obtained to determine the pressure drop of the gas-liquid layer on dual-flow plates. Plates were studied on model system «water – air». Free cross-section of plates was 16, 25 and 36 %, a diameter of the holes of plates was 0.012 m, diameter of the plates was 0.15 m

Research of local gas content of gas-liquid layer for different operating regimes of dual-flow plates

Проведены измерения локального газосодержания на тарелке провального типа для режима однородного барботажного слоя и режима подвижного газожидкостного слоя кондуктометрическим способом. Определены фрактальные размерности графиков зависимости локального газосодержания от высоты установки датчика от плато тарелки. Установлено наличие аттрактора гидравлического сопротивления тарелки для режима подвижного газожидкостного слоя

Determination of local gas content of gas-liquid layer by conductometric method

It is proposed a method for measuring local gas content values by conductometric method. The design of the sensor for measurement of local values of gas content is proposed. Electric scheme of its connection is proposed. Parameters of circuitry elements are proposed. Method of calculating the resistance of the sensor is proposed. It was done calibration of the sensor, on the basis of which it is proposed calculation of the local values of gas content

Rotary Entrainment in Two Phase Stratified Gas-Liquid Layers:An Experimental Study

Rotary Entrainment in Two Phase Stratified Gas-Liquid Layers:An Experimental Study

Study on the Inter-electrode Process of Aluminum Electrolysis

The voltage distribution between carbon anode and aluminum cathode in cryolite electrolyte saturated with alumina was determined using a scanning reference electrode to investigate the inter-electrode process during aluminum electrolysis. The results showed that the anode–cathode-distance (ACD) is consisted of three parts: a relatively stable cathode boundary layer, bubble-free electrolyte layer, and gas–liquid layer near the anode. The aluminum diffusion layer with high electronic conductivity as well as the crystallization of cryolite was observed at the cathode boundary layer. The thickness of the aluminum diffusion layer varied with current density, which further determined the critical ACD. The thickness, coverage, and releasing frequency of the bubbles on both laboratory and industrial prebaked cells were derived, and it is found that the average bubble coverage decreases with current density, and the average coverage at 0.8 A cm−2 is approximately 50 pct.

Rotary Entrainment in Two Phase Stratified Gas-Liquid Layers: An Experimental Study

Rotary Entrainment in Two Phase Stratified Gas-Liquid Layers: An Experimental Study

Vortical Contact Stage for Heat- and Mass-Exchange Processes

The schematic of a vortical contact stage is presented for heat- and mass-exchange processes, and possible flow regimes of the gas-liquid layer are analyzed. Equations for calculation of the critical gas velocity ensuring conversion to an annular flow regime of the gas–liquid mixture, and relationships between the Sherwood and Reynolds numbers are derived. The Murfree efficiency of the vortical contact stage is evaluated. Relationships between the coefficient of convective heat exchange during boiling in the rotating layer on the specific heat load and centrifugal criterion are obtained.

Liquid entrainment behavior at the nozzle exit in coaxial gas–liquid jets

The near-field flow behavior of coaxial gas–liquid jets has a significant influence on the atomization performance and life cycle of atomizers, and the present study focused on this issue. The flow visualization technique was employed to examine liquid entrainment behavior near the nozzle. The thick central tube affected both gas and liquid flow fields. Liquid entrainment could be observed in the near-field with the increase in gas velocity, and a liquid “bulge” structure was induced on the surface of the near-field liquid jet for the first time. The formation mechanism and dynamic characteristics of the “bulge” were studied. Two critical situations in the liquid entrainment process to the surface of the central tube were identified as “initial entrainment” and “full entrainment”. The two critical situations were studied in a convective gas–liquid layer in the recirculation region based on total pressure conservation theory. The theoretical models for the two situations were obtained, and these models agreed well with the experimental results.

Structure of Gas-liquid Layer in a Section Sparger

A study of the structure of the gas–liquid layer beneath a section baffle plate in a section sparger is presented. A model that defines the dependence of the mean surface-volume diameter of gas bubbles on the magnitude of the gas content is developed on the basis of the theory of locally isotropic turbulence. The results of experiments confirmed the goodness-of-fit of the proposed model.

Local characteristics of a gas-liquid layer in a sectionalized bubble reactor

The results of experimental study of local properties of a gas-liquid system in a sectionalized bubbler-type reactor are reported. The radial profiles of local gas content, specific phase contact surface, gas bubble tracking frequency, and average bubble diameter are studied for different gas and liquid flow rates and reactors having different geometric parameters. Conclusions are drawn regarding the pattern and causes of variation of these properties. The derived data was used at OOO LUKOIL-Permnefteorgsintez to upgrade oxidation columns for petroleum asphalt production.

Change in drag, apparent slip and optimum air layer thickness for laminar flow over an idealised superhydrophobic surface

AbstractAnalytic results are derived for the apparent slip length, the change in drag and the optimum air layer thickness of laminar channel and pipe flow over an idealised superhydrophobic surface, i.e. a gas layer of constant thickness retained on a wall. For a simple Couette flow the gas layer always has a drag reducing effect, and the apparent slip length is positive, assuming that there is a favourable viscosity contrast between liquid and gas. In pressure-driven pipe and channel flow blockage limits the drag reduction caused by the lubricating effects of the gas layer; thus an optimum gas layer thickness can be derived. The values for the change in drag and the apparent slip length are strongly affected by the assumptions made for the flow in the gas phase. The standard assumptions of a constant shear rate in the gas layer or an equal pressure gradient in the gas layer and liquid layer give considerably higher values for the drag reduction and the apparent slip length than an alternative assumption of a vanishing mass flow rate in the gas layer. Similarly, a minimum viscosity contrast of four must be exceeded to achieve drag reduction under the zero mass flow rate assumption whereas the drag can be reduced for a viscosity contrast greater than unity under the conventional assumptions. Thus, traditional formulae from lubrication theory lead to an overestimation of the optimum slip length and drag reduction when applied to superhydrophobic surfaces, where the gas is trapped.

Simulation of heat and mass exchange in foam apparatus at high moisture content in vapor-gas mixture

Calculated data have been obtained that reflect transient temperature changes in fluid and in the moisture content in the foam layer of a bubbling apparatus. The mass-transfer processes were found to occur at higher moisture contents, which have a significant effect on heat transfer. The effect of the Stefan flow on the values of the moisture content of air treated in a foam layer was observed. The calculations were performed for steady-state parameters of the gas-liquid layer, i.e., the coefficients of interphase heat and mass return. The calculation results were compared with the known experimental data. The approximate formulas have been obtained for determining the coefficients of interphase heat and mass return at a constant temperature of the coolant.

Mass transfer in gas-liquid layer on vortex contact stages

The results of studying mass transfer in a gas-liquid layer on vortex contact stages with tangential swirlers are presented. Relationships for calculating the mass transfer coefficients and Murphree efficiency are derived.

Corona Discharge to Water Surface and Its Transition to a Spark

Impulse corona discharge in atmospheric air to the surface of a water layer with different electric conductivities is studied. The discharge was initiated from a corona electrode consisting of a metallic disk with evenly distributed corona needles. The dependences of the magnitudes of the measured impulse currents on the polarity of the corona electrode as well as the parameters of the gas gap and liquid layer were obtained. An equivalent electric circuit of the discharge system was proposed, allowing for explanations of the regularities in the measured currents and also the role of the water layer as a factor affecting the transition of the corona discharge to a spark.

ЗакономерностИ гИдродИнамИкИ пеннОгО слоЯ сО стабилизатороМ

The basic laws of hydrodynamics of a foam layer with a stabilizer on the small hole antiexact plate are developed. The structural parameters of phases of foamy layer are examined as a continuous environment. Take into account the mutual influence of two phases. The vibrations of gas-liquid layer are studied

Two-dimensional problem of the impact of a vertical wall on a layer of a partially aerated liquid

The two-dimensional unsteady problem of the impact of a vertical wall on a layer of a liquid which is mixed with air near the wall and does not contain air bubbles away from the wall is solved in a linear approximation. The gas-liquid mixture is modeled by a homogeneous, ideal, and weakly compressible medium with a reduced sound velocity dependent on the air concentration in the gas-liquid mixture. Outside the gas-liquid layer, the liquid is considered ideal and incompressible. During the initial stage of the impact, the liquid flow and the hydrodynamic pressure are determined using the linear theory of the potential motion of an inhomogeneous liquid. The dependence of the amplitude of the impact pressure along the wall on the air concentration in the gas-liquid layer and on the thickness of this layer is investigated. For a small relative thickness of the layer, the thin-layer approximation is used. It is shown that the solution of the original problem tends to the approximate solution as the thickness of the layer decreases. It is shown that the presence of the gas-liquid layer leads to wall pressure oscillations. Estimates are obtained for the pressure amplitude and the oscillation period.

Rigorous modelling of [formula omitted] absorption in tray and packed columns

The absorption of NO x into pure water or nitric acid is usually a kinetically controlled operation in which complex reactions in both gas and liquid phases are combined with multicomponent mass transfer. To be able to describe this process adequately, a rigorous general rate-based model for the reactive absorption in tray and packed columns has been developed based on earlier works (see, e.g. [Kenig et al., 2001. Chemical Engineering Science 56, 343–350; Kenig et al., 2003. Chemical Engineering and Technology 6, 631–646]). Heat and multicomponent mass transfer in the film phases, chemical reactions and thermodynamic non-idealities are taken into account. Furthermore, the influence of column internals and hydraulics is considered via relevant correlations. For tray columns, a special consideration of the empty sections above the gas–liquid layer on a tray is included. The model is implemented into the simulation environment Aspen Custom Modeler TM and validated by comparison with experimental data for a pilot scale packed column and an industrial sieve tray column equipped with cooling coils. The simulation results obtained for both column types agree well with the experimental measurements. In addition, the influence of cooling on the process behaviour is studied.