Cavitation Tube Research Articles

Removal of algae using hydrodynamic cavitation, ozonation and oxygen peroxide: Taguchi optimization (case study: Raw water of sanandaj water treatment plant)

Algal blooms can have both direct and indirect harmful impacts on water quality, resulting in changes in coloration, unpleasant taste and odor, turbidity, and During such blooms, algae cells may produce and release unpleasant algal metabolites such as taste and odor-causing compounds and cyanotoxins, which can have adverse impacts on water quality. The purpose of this study is to remove of dominant algae from water entering the water treatment plant of Sanandaj using Hydrodynamic Cavitation, Ozonation, and Hydrogen peroxide and process optimization using the Taguchi design method. Seven parameters that are effective in Algae Removal, including pH, retention time, Cavitation pressure, flow, The distance of the orifice plate from the beginning of the cavitation tube, Ozone concentration, and Hydrogen peroxide concentration, were selected as the major factors; Each factor has three levels. the optimal conditions for removal of Melosira and Oscillatoria are the Cavitation pressure: 5 bar, the Retention Time: 90 min, pH: 5, the Flow: 1 m3/s, The distance of the orifice plate: 25 cm, the Ozone rate: 3 gr/h, Hydrogen Peroxide: 2 gr/l. Based on the percentage portion of each factor, the Cavitation Pressure was introduced as the most effective factor in the removal of the Melosira and the Oscillatoria (38.16% and 35.76%, respectively). Hydrodynamic cavitation presents great potential to treat eutrophic water bodies due to the high efficiency shown in microalgae inactivation. Moreover, hydrodynamic cavitation represents a sustainable removal technique, since it does not produce secondary pollution.

Iron Ore Slimes Flotation Tests Using Column and Amidoamine Collector without Depressant

This work describes the concentration of iron ore slimes on a pilot scale by using a 500-mm diameter flotation column and a novel collector, which renders the use of a depressant unnecessary. The pilot column was operated in series with the industrial plant Vargem Grande 2 (Iron Quadrangle, Brazil) receiving, as feed, part of the underflow from the desliming thickener. These pilot tests represented only the rougher stage of a flotation circuit. The novel collector used was an amidoamine (average collector dosage of 160 g/t), and the tests were carried out in the absence of starch, at pH 10.5 and with bubbles/microbubbles generated by cavitation tube. It was possible to achieve a concentrate, by reverse flotation, with an average iron content of 53% and an average metallurgical recovery of 91.5% The recovery of the silica in the froth was 53.1% in average for one stage of flotation. The high variability of the slime characteristics rendered difficult the stabilization of the SiO2 recovery; however, the applicability of the amidoamine collector was proven. In an industrial scale circuit, the use of online analyzers for Fe and SiO2 content and the adoption of control logics based on the adjustment of parameters such as reagents dosage and washing water flow rate adjustment should contribute to the optimization of the results obtained in the pilot scale tests. Further studies adding a cleaner concentration stage should be performed.

An experimental study on size distribution and zeta potential of bulk cavitation nanobubbles

Nanobubble flotation technology is an important research topic in the field of fine mineral particle separation. The basic characteristics of nanobubbles, including their size, concentration, surface zeta potential, and stability have a significant impact on the nanobubble flotation performance. In this paper, bulk nanobubbles generated based on the principle of hydrodynamic cavitation were investigated to determine the effects of different parameters (e.g., surfactant (frother) dosage, air flow, air pressure, liquid flow rate, and solution pH value) on their size distribution and zeta potential, as measured using a nanoparticle analyzer. The results demonstrated that the nanobubble size decreased with increasing pH value, surfactant concentration, and cavitation-tube liquid flow rate but increased with increasing air pressure and increasing air flow rate. The magnitude of the negative surface charge of the nanobubbles was positively correlated with the pH value, and a certain relationship was observed between the zeta potential of the nanobubbles and their size. The structural parameters of the cavitation tube also strongly affected the characteristics of the nanobubbles. The results of this study offer certain guidance for optimizing the nanobubble flotation technology.

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands—II. Flotation hydrodynamics of water‐based oil sand extraction

AbstractBitumen flotation hydrodynamics in water‐based oil sand extraction is critically reviewed by comparing aeration of oil sand slurries with mineral flotation. The role of the two‐stage particle‐bubble attachment model in flotation is emphasized as a means to accelerate bitumen flotation recovery. It involves the generation of micro/nanobubbles and their frosting on hydrophobic bitumen droplets, followed by their attachment to a flotation‐size bubble via its coalescence with the nanobubbles frosted on the bitumen. Nanobubble generation by hydrodynamic cavitation demonstrates that the size of nanobubbles can be reduced, and the number of nanobubbles increased by fast liquid flow, intensified agitation, high dissolved gas content and surfactant concentration. The mechanism of pre‐existing gas nuclei in enhancing nanobubble generation by cavitation is utilized to produce a large volume of stabilized nanobubbles for practical flotation, by continuously recirculating the stream through a gas saturation tank or a cavitation tube. The aeration of oil sand slurries in hydrotransport pipelines is analyzed based on its similarity to dissolved air flotation. Bitumen extraction recovery increased significantly with the presence of nanobubbles in the system. The role of improved flotation hydrodynamics in bitumen recovery is briefly discussed in terms of the Suncor operation using flotation columns to process oil sand middling streams. Future research should be directed at understanding bitumen flotation kinetics, optimizing size ranges of nanobubbles for maximized flotation recovery, minimizing wearing of cavitation tubes in industrial operations, and intensifying the role of in‐situ nanobubble nucleation on hydrophobic particles/bitumen droplets in flotation, especially for bitumen extraction from underperforming oil sands.

A Comparative Study of Different Columns Sizes for Ultrafine Apatite Flotation

The desliming operation to discharge ultrafine particles less than 20 µm prior to concentration by flotation is a common practice in phosphate ores beneficiation plants. The first industrial application for the beneficiation of the phosphate material with particle sizes <44 µm in Brazil was in the Araxá plant concentrator in the beginning of the 1980s. This work shows the comparative flotation results with two different phosphate slime samples (<40 µm) obtained from the Copebras (CMOC International) industrial plant located in Catalão (Goiás state, Brazil), considering a circuit with rougher/cleaner configuration with different columns sizes, as follows: Circuit 1 (rougher—4” diameter column; cleaner—2” diameter column) and circuit 2 (rougher—6” diameter column; cleaner 4” column). The results indicate that better flotation apatite recovery results were achieved for the circuit with higher size columns (6” and 4”). The results can be explained by the application of a cavitation tube in the rougher stage in the 6” column. The improved flotation performance can be attributed to increased probabilities of collision and attachment and the reduced probability of detachment by the small size bubbles generated by the cavitation tube in comparison with the bubbles produced by the porous tube of the 4” column flotation.

Nanobubbles generation in a high-rate hydrodynamic cavitation tube

Gas dispersion parameters (air holdup-ɛg, superficial air velocity-Jg and bubble surface area flux-Sb) and especially the concentration of formed nanobubbles in a hydrodynamic cavitation tube were measured. Best results were obtained at 30% air/liquid volume ratio; 49 mN m−1 air/liquid interfacial tension resulting in an air holdup of 16%, a Jg of 0.87 cm s−1, a Sb of 85 s−1 and a nanobubbles (230–280 nm) concentration of 6.4 × 108 NBs mL−1. The lower the air/liquid interfacial tension, the higher the air holdup; this proceed by assisting cavitation and formation of micro and nano-sized bubbles. Data obtained are discussed in terms of solution, hydrodynamics and interfacial phenomena. Main mechanisms involving the role of the nanobubbles and their interactions with solids and bigger bubbles were envisaged. It is believed that these findings are important because of the need for techniques and devices producing nanobubbles at low cost and high rate. This work shows that the cavitation tube studied has a high potential, due to the wide size of bubbles formed, high bubble surface flux obtained and especially the generation of a high concentration of nanobubbles. These bubbles are very important in modern flotation of mineral fines and in pollutant separation in wastewater treatment and some examples are shown and discussed.

A GPU based compressible multiphase hydrocode for modelling violent hydrodynamic impact problems

This paper presents a GPU based compressible multiphase hydrocode for modelling violent hydrodynamic impacts under harsh conditions such as slamming and underwater explosion. An effort is made to extend a one-dimensional five-equation reduced model (Kapila et al., 2001) to compute three-dimensional hydrodynamic impact problems on modern graphics hardware. In order to deal with free-surface problems such as water waves, gravitational terms, which are initially absent from the original model, are now considered and included in the governing equations. A third-order finite volume based MUSCL scheme is applied to discretise the integral form of the governing equations. The numerical flux across a mesh cell face is estimated by means of the HLLC approximate Riemann solver. The serial CPU program is firstly parallelised on multi-core CPUs with the OpenMP programming model and then further accelerated on many-core graphics processing units (GPUs) using the CUDA C programming language. To balance memory usage, computing efficiency and accuracy on multi- and many-core processors, a mixture of single and double precision floating-point operations is implemented. The most important data like conservative flow variables are handled with double-precision dynamic arrays, whilst all the other variables/arrays like fluxes, residual and source terms are treated in single precision. Several benchmark test cases including water-air shock tubes, one-dimensional liquid cavitation tube, dam break, 2D cylindrical underwater explosion near a planar rigid wall, 3D spherical explosion in a rigid cylindrical container and water entry of a 3D rigid flat plate have been calculated using the present approach. The obtained results agree well with experiments, exact solutions and other independent numerical computations. This demonstrates the capability of the present approach to deal with not only violent free-surface impact problems but also hull cavitation associated with underwater explosions. Performance analysis reveals that the running time cost of numerical simulations is dramatically reduced by use of GPUs with much less consumption of electrical energy than on the CPU.

A compressible single‐temperature conservative two‐phase model with phase transitions

SUMMARYA model for multidimensional compressible two‐phase flow with pressure and velocity relaxations based on the theory of thermodynamically compatible system is extended to study liquid–gas flows with cavitation. The model assumes for each phase its own pressure and velocity, while a common temperature is considered. The governing equations form a hyperbolic system in conservative form and are derived through the theory of a thermodynamically compatible system. The phase pressure‐equalizing process and the interfacial friction are taken into account in the balance laws for the volume fractions of one phase and for the relative velocity by adding two relaxation source terms, while the phase transition is introduced into the model considering in the balance equation for the mass of one phase the relaxation of the Gibbs free energies of the two phases. A modification of the central finite‐volume Kurganov–Noelle–Petrova method is adopted in this work to solve the homogeneous hyperbolic part, while the relaxation source terms are treated implicitly. In order to investigate the effect of the mass transfer in the solution, a 1D cavitation tube problem is presented. In addition, two 2D numerical simulations regarding cavitation problem are also studied: a cavitating Richtmyer–Meshkov instability and a laser‐induced cavitation problem. Copyright © 2014 John Wiley & Sons, Ltd.

Finite volume simulation of unsteady shock‐cavitation in compressible water

SUMMARYThe present paper extends an established Riemann‐based finite volume hydrocode for compressible pure water to admit change of phase. The thermal and caloric behaviour of water and water vapour is described by a one‐fluid model on the assumption that the two‐phase regime can be described locally within a finite volume cell as a homogeneous mixture that remains in thermodynamic equilibrium. Closure of the equation set is achieved by deriving equations of state for pure fluids and the mixture that cover all possible fluid states. Following a description of the flow model and the numerical method, computations are carried out to demonstrate the potential of the method. Calculations include a one‐dimensional cavitation tube, one‐dimensional condensation front, collapse of a cavitation bubble in water in one dimension, and an unsteady two‐dimensional hypervelocity flow past a cavitating hydrofoil. Copyright © 2012 John Wiley & Sons, Ltd.

Degradation of C.I. Reactive Red 2 through photocatalysis coupled with water jet cavitation

The decolorization of an azo dye, C.I. Reactive Red 2 was investigated using TiO 2 photocatalysis coupled with water jet cavitation. Experiments were performed in a 4.0 L solution under ultraviolet power of 9 W. The effects of TiO 2 loading, initial dye concentration, solution pH, geometry of cavitation tube, and the addition of anions on the degradation of the dye were evaluated. Degradation of the dye followed a pseudo-first order reaction. The photocatalysis coupled with water jet cavitation elevated degradation of the dye by about 136%, showing a synergistic effect compared to the individual photocatalysis and water jet cavitation. The enhancement of photocatalysis by water jet cavitation could be due to the deagglomeration of catalyst particles as well as the better contact between the catalyst surfaces and the reactants. Venturi tube with smaller diameter and shorter length of throat tube favored the dye decolorization. The degradation efficiency was found to increase with decreasing initial concentration and pH. The presence of NO 3 − and SO 4 2− enhanced the degradation of RR2, while Cl −, and especially HCO 3 − significantly reduced dye decolorization. The results of this study indicated that the coupled photocatalysis and water jet cavitation is effective in degrading dye in wastewater and provides a promising alternative for treatment of dye wastewater at a large scale.

Nanobubble generation and its application in froth flotation (part I): nanobubble generation and its effects on properties of microbubble and millimeter scale bubble solutions

A special nanobubble generation system has been developed for evaluating the effect of nanobubble on froth flotation. In this study, an eight-factor five-level Central Composite Experimental Design was conducted for investigating eight important parameters governing the median size and the volume of nanobubbles. These process parameters included surfactant concentration, dissolved oxygen (O 2) content, dissolved carbon dioxide gas (CO 2) content, pressure drop in cavitation tube nozzle, <50 nm hydrophobic particle concentration, <50 nm hydrophilic particle concentration, slurry temperature and the time interval after nano- bubble generation. The properties, stability and uniformity of nanobubbles were investigated. The study of the produced nanobubble's effects on the characteristics of microbubble solutions and millimeter scale bubble solutions was performed in a 50.8 mm column.

The Effects of Jet Cavitation on the Growth of Microcystis Aeruginosa

Different operating factors of jet cavitation method affecting one of cyanobacterial's (Microcystis aeruginosa) growths were investigated. The inhibition on M. aeruginosa growth by the jet cavitation method depended strongly on the hydraulic characteristics of cavitation tube, inlet pressure, cavitation number, light and different algae concentrations. The inhibitive efficiency of 64.58% in field water sample was obtained by this method. Moreover, the ultrastructural changes of M. aeruginosa before and after treatment were observed by the transmission electron microscope (TEM). The changes of UV-Visible spectra further demonstrated the inhibitive behaviors of jet cavitation on the growth of M. aeruginosa. The experimental results showed that jet cavitation method was a potential physical technology that could effectively inhibit the growth of M. aeruginosa.

Numerical and experimental study of a hydrodynamic cavitation tube

A numerical analysis of hydrodynamics in a cavitation tube used for activating fine particle flotation is described. Using numerical procedures developed for solving the turbulent k-ɛ model with boundary fitted coordinates, the stream function, vorticity, velocity, and pressure distributions in a cavitation tube were calculated. The calculated pressure distribution was found to be in excellent agreement with experimental results. The requirement of a pressure drop below approximately 10 m water for cavitation to occur was observed experimentally and confirmed by the model. The use of the numerical procedures for cavitation tube design is discussed briefly.

Relative Flotation Response of Zinc Sulfide: Mineral and Precipitate

ABSTRACT A study has been conducted to compare the floatability of fine zinc sulfide (ZnS) precipitates and sphalerite particles. The floatability of the precipitates was significantly poorer compared to sphalerite particles when xanthate was used as the collector. The floatability was improved by using dodecylamine as the collector, and the difference in floatability between the precipitates and sphalerite particles was reduced. The flotation kinetics of the precipitates was further improved significantly by incorporating a hydrodynamic cavitation tube in a conventional (mechanical) flotation cell. The improved kinetics was attributed to in-situ gas nucleation on the precipitates.