Air-lift Performance Research Articles

Detailed 3D URANS analysis of two-phase flow in an airlift pump

An airlift pump is a vertical tube that utilizes the buoyant effects of a gas to lift a liquid. Unlike a standard mechanical pump, the liquid flow rate through the airlift pump is not directly controlled; rather, it depends on the supplied gas flow rate, the tube length and diameter, and the relative height of the liquid supply free surface (submergence ratio). The present study uses the commercial CFD code ANSYS CFX to model the isothermal, 3D, transient flow in an airlift pump using water and air. The model applies pressure boundary conditions at both ends of the tube and specifies the mass flow rate of air through multiple openings in the side of the tube. The bottom of the tube is an inlet of water only and the outlet is a two-phase flow opening. A time-dependent, homogeneous, VOF two-phase RANS CFD modelling approach is used with the air treated as an ideal gas. This work found that a complete 3D domain was necessary for consistent prediction of the airlift performance and physically realistic two-phase flow structures. Statistical analysis of the two-phase flow structures was applied to characterize airlift pump instability and better understand the physics of the airlift pump.

Oxygen transfer and gas holdup in airlift bioreactors assembled with helical flow promoters.

Bioreactors can perform biochemical conversions mediated by biocatalysts, such as enzymes, animal cells, plants, and microorganisms. Among several existing models, airlift bioreactors are devices with the low shear environment and good mass transfer with low energy consumption, employed in several biochemical processes. The fluid flow is enabled through air injection by the sparger located at the bioreactor base. Despite its simple geometry compared with the conventional bioreactors, airlift performance can be optimized via geometrical modifications. Therefore, the objective of this work was to evaluate the effects of the addition of helical flow promoters, positioned in the riser and/or downcomer regions of an airlift of concentric tubes measuring the volumetric oxygen coefficient (kLa) and gas holdup. The results obtained by varying the gas flow rate from 1.0 to 4.0 vvm allowed the system evaluation of oxygen transfer and gas holdup. The inclusion of helical flow promoters increased the kLa, reaching up to 23% in oxygen transfer compared to tests without helicoids and up to 14% increase in the gas holdup. The inclusion of helical flow promotors was beneficial for all gas flow rates. Thus, including these flow promoters is an effective strategy to increase the oxygen transfer rate for bioprocess optimization.

200 m立型水槽を用いたエアリフト実験について

In this paper, the study on the performance of a 200 m airlift pump for water and highly-viscous shear-thinning slurry is introduced, mainly following the published paper [1]. The experiment was conducted using the facility in Advanced Institute of Science and Technology, Tsukuba, which had been used for the project of polymetallic nodule about 30 years ago. Here, in the present study, we investigate the airlift performance for the shear-thinning slurry which imitates the rare-earth mud water in the deep ocean. The experimental results showed that the airlift pump can work properly not only for water but also highly viscous slurry. It was confirmed that actual airlift performance obtained with the experiments does not show the reduction of the lifted liquid with increasing the gas flow rate, which the numerical results show the some deviation of the predicted value for high gas flow rate.

Experimental Evaluation of Airlift Performance for Vertical Pumping of Water in Underground Mines

This paper presents experimental studies on the optimization of air–water flow in an airlift pump. Airlift pumps use compressed gas to verticall transport liquids and slurries. Due to the lack of theoretical equations for designing and predicting flow regimes, experimental investigations must be carried out to find the best condition to operate an airlift pump at high efficiency. We used a new air injection system and different submergence ratios to evaluate the output of a simple pump for vertical displacement of water in an underground mine. The tests were carried out in a new device with 5.64 m height and 10.2 cm circular riser pipe. Three air-jacket pipes, at different gas flows in the range of 0.002–0.09 m3/s were investigated with eight submergence ratios. It was found that with the same air flow rate, the most efficient flow of water was achieved when an air jacket with 3 mm diameter holes was used with a submergence ratio between 0.6 and 0.75. In addition, a comparison of practical results with two theoretical models proposed by other investigators showed that neither was able to accurately predict airlift performance in air–water flow mode.

Modeling of multiphase flow at solid particles hydropelling

Purpose. Development of methods for calculating the parameters of the solid particles lifting from the bottom of reservoirs based on the three-phase (gas-liquid-solid particles) flow simulation in an air-lift pipe. Methodology. Mathematical modeling of multiphase flows based on hydraulic ratios. In doing so, heights of up to 10 m (short airlift) are considered with corresponding physical assumptions. Findings. A methodological support has been developed for calculating rational parameters of modes of transporting solid particles with a short airlift. The solution of the problem of the solid particles hydraulic lift by a short airlift is reduced to solving a system of nonlinear algebraic equations. Parametric calculations were carried out and the dependences of the gas flow rate required to ensure a given airlift performance were determined, and the influence of the geometric characteristics of the pipelines on the flow of the solid phase was estimated. Originality. The proposed method allows one to determine the parameters of the solid particles hydraulic lift in a short airlift by solving a system of nonlinear algebraic equations, without using the apparatus of mathematical physics methods. Practical value. It consists in the development of a method for calculating and determining rational parameters of pulp transportation processes in short airlifts. These methods make it possible to determine the dependence of the air flow on the solid particles flow and substantiate the corresponding geometric and flow parameters of the hydraulic lift system. Key words: short airlift, multiphase flow, solid particles hydraulic lift, technological calculatio.

Effect of Air Injector on the Airlift Performance in Air-Water-Solid Three-Phase Flow

AbstractTo understand the effect of an air injector on airlift performance, an experimental study of the influence of air exit-port arrangement on the mass flow rate of solids and lifting efficiency was performed. An airlift with a riser 1,500-mm long and 40-mm diameter was designed and tested. At a constant submergence ratio, the mass flow rate of solids and lifting efficiency were significantly affected by the air exit-port arrangement. As the air flow rate increased, the mass flow rate of solids increased to a maximum value and then decreased slightly. The curve relating the air flow rate to lifting efficiency was m-shaped, i.e., it contained two local maxima. The air flow rate at the second efficiency maximum was approximately equal to the air flow rate at which the solid mass flow rate was maximal. When the measurement results were expressed in dimensionless form, the relation between the volume flow of slurry and air flow rate was approximately the same for all air exit-port arrangements, and was in...

The Effect of Air Injection Method on the Airlift Pump Performance

With simple structure, excellent reliability, low cost, no restriction at depth of water, and easy control and operation, airlift pumps have special advantage in borehole hydraulic jet mining, river dredging and deep sea mining. To clarify the mechanism and process of action of air injection methods on air lift performance, and to enhance lifting capacity, the pump performance of a small airlift system in transporting river sands is investigated experimentally in the present study. The results are as the follows. The influences of air exit ports on water volume flow rate, mass flow rate of solids and lifting efficiency are studied and found to be very low when the number of air exit ports exceeds 3. The pump design show best pumping capability for water and solids at higher air flow rates, but the lifting efficiency is then very low. In addition, a dimensionless equation which describes the flows in the pipe is presented based on the Bernoulli equation, and compared with measurement results in the dimensionless form, which are nearly in good agreement with each other for all the arrangements of air exit ports and are basically contained within ±18% of the theoretical curve. The results are important for understanding the mechanism of airlift pumps and enriching multiphase flow theory.

The Effect of Air Injector on the Performance of Airlift

In order to investigate the air injection method on the performance of an airlift. For this purpose an air lift system with a riser 2000 mm long and 80 mm in diameter, was designed and tested. Seven different air injection methods were used at a constant submergence. The experimental results showed a marked effect on the airlift performance when operated with different air injection methods. The arrangement of five nozzles gives the best performance, and the one nozzle is the worst. Although the injection angle has a little effect on the airlift performance, but view the general conclusions as a whole, the best lifting efficiency can be obtained when the angle of the nozzle placed along the tangential direction of pipe wall is equal to 10º at a given air flow rate QG =37m3/h.

Effect of operating conditions and particle properties on performance of vertical air-lift

The effect of the fluidization air flow rate and the transport air velocity on the solids mass flow rate and the pressure drop along the transport pipe was investigated in a vertical air-lift. The use of two different materials, glass (150μm) and zirconium oxide (260μm) particles (Geldart's B class), enabled to estimate the effect of particle properties on the air-lift performance. Different levels of the solids mass flow rate were obtained by varying the fluidization air flow rate while keeping the transport air velocity constant. The solids loading ratio varied between 2 and 16 for both types of particles. The pressure drop was non-linearly related to the solids mass flow rate at most of the transport air velocities tested. State diagrams presenting the relationship between the transport air velocity, the solids mass flow rate, and the pipeline pressure drop were constructed to characterize the flow pattern and to compare the behavior of the glass and zirconium oxide particles. Owing to the larger size and higher density, the zirconium oxide particles displayed higher pressure drop values than the glass beads and the minimum pressure drop shifted towards higher transport air velocities. The velocity at the transition between dilute and dense phase conveying was approximately in the range of 7 to 10m/s for glass beads and 10 to 12m/s for zirconium oxide, at the solids mass flow rates tested. The flow patterns could be also effectively characterized from the analysis of the pressure drop fluctuations at different transport air velocities.

Effect of Air Injector on the Performance of an Air-lift for Conveying River Sand

An air-lift has been more recently applied in the dredging, deep-seated beach placer mining and underground mining engineering. However, the influence and mechanism of various parameters on the air-lift performance are not quite clear, especially the influence of flow pattern on lifting efficiency. Focusing on the problems mentioned above, the key part of the air-lift (namely, the air injector) was proposed aimed to reduce friction loss in the inner pipe according to improving flow field performance, thus increase the lifting efficiency. The study of relative factors of the performance of an air-lift is performed and the river sand is used as simulation of underground ore bed. The total lifting height of the experimental system is 3 m, the water flux, mass flow of solid particles, concentration of particles and lifting efficiency are measured under the same submergence ratios by changing the air injector, which is divided into nine specifications of air injection in this research. The experimental results indicate that the optimal air flow rate corresponding to excellent performance of the air-lift can be obtained in the range of 35–40 m3/h. The air injection method has a great effect on the performance of the air-lift, the air injector with three nozzles is better than that in the case of one or two nozzles. Further more, the air injection angle and arrangement of air injection pipes also have great effect on the performance of an air-lift. The proposed research results have guiding significance for engineering application.

Evaluation of air-lift pump capabilities for water delivery, aeration, and degasification for application to recirculating aquaculture systems

A methodology is demonstrated for evaluating the feasibility of using air-lift pumps for water movement, aeration, and degasification in a recirculating aquaculture system. A set of empirical equations are presented modeling the performance of a 5.08-cm (2″) diameter air-lift submerged 91.44 cm (36″) with a 15.24-cm (6″) lift operated at 28–142 l min −1 (1–5 scfm) of air injection. A steady state mass balance on oxygen and carbon dioxide, equating the system requirements to the air-lift capabilities is illustrated. Using the empirical relationships developed and standard methods to estimate system O 2 demand and CO 2 production, equations are derived to calculate steady state DO and DC concentrations for any number of air-lifts used in a given recirculating system. The predicted air-lift performance in a typical system indicates the water delivery capacity for low head applications is significantly above the gas exchange capabilities. It is recommended that air-lifts be designed for water delivery and that the demonstrated methodology be used to estimate their supplemental aeration and degasification performance. Open-water aeration is shown to be more energy efficient than aeration using air-lifts. The data suggests that, for blown air systems, when the aeration requirements are met, the carbon dioxide stripping requirements are also. Suggestions for designing recirculating systems utilizing air-lifts are also presented.

Stability of small diameter airlift pumps

In an airlift pumping process, air is injected into the pipe containing the fluid to be transferred. Small diameter airlift pumps are, in particular, used for corrosive or radioactive liquids. However, for certain combinations of the geometrical parameters and air flow rate, they may become unstable. In this case, the flow at the riser outlet pulsates strongly, which cannot be accepted for many applications. An airlift pump involves three different regions, e.g. a single phase liquid flow and a separate single phase gas flow upstream of the air injection device and a two-phase flow downstream. The instabilities are due to density wave oscillations in the two-phase flow. Depending on the liquid flow inertia, friction effects and gas flow compressibility, the density waves are sustained or not. The present study is based upon a detailed description of the steady state flow in a small diameter airlift pump. A linear stability analysis is performed and assessed against an extensive set of experimental data. Both the experimental and analytical results show that the influencing parameters have complex effects and strongly interact: the same variation of a parameter may have opposite effects, i.e. stabilizing or destabilizing, depending on the values of the other parameters. The effect of the compressibility of the gas flow between the regulating valve and the air-injection device is shown to be very important. The analysis presented leads to a numerical model that can be considered as a practical tool for airlift performance and stability analysis.

A Study of Airlift for the Feeder of Solids

Some experimental and theoretical studies of airlift, which is used for a feeder of particles in the pneumatic conveyance system are described. The feeding performances are obtained experimentally using several kinds of particles, and pressure losses in airlift are analysed to estimate the power required; which are compared with experimental ones. The drag coefficients of particles in a fully developed turbulent pipe flow are determined experimentally to make an accurate calculation of the pressure losses. The feeding performance of airlift can be represented by formulae using the results of a simple discharge test of particles from a two-dimensional port. The agreement of the calculated pressure losses with experimental ones is quite good when the calculation is made using the drag coefficient of particles obtained in the test.