Flotation Tanks Research Articles

Analytical Solution for Optimum Design of Nozzle Discharge Lines Based on Hydraulic Considerations

This study focuses on finding the best design of nozzles used in the water discharge pipelines delivering free jets based on hydraulic considerations. An analytical solution is carried out to determine the best design for these nozzles. The solution depends on the derivative method applied to the energy head concerning the nozzle diameter to maximize the power of the jet. The equation derived for computing the best pipe-nozzle diameter ratio D/d in discharge lines applies over practical ranges of relative distance L/D (50-500) and relative roughness e/D (0.01-0.05). An illustrative example is solved and gives D/d = 1.8858 (closely equal to 1.9), the deviation is 0.77%, which is firmly accepted. The equation holds good for D/d from 1.4 to 3.584 and could be applied to compute D/d ratios without the need for a computer program. In the derived equation, D/d is a function of relative distance L/D, and friction factor F with negligible computational errors. The derived equation when compared with the conventional one, shows an increase in the computed power of the jet ranging from 12.5 to 19.23%. The evaluation study reflects the rigidity of the derived equations and their reliability in computing the best pipe-nozzle diameter ratios in discharge lines delivering free jets with reasonable powers, while the conventional formula is approximate. However, many engineering applications of water jet nozzles are used in; impulsive turbines, power-delivering free jets, water filters, flotation tanks, sedimentation tanks, water storage tanks, trickling filters, and other water and wastewater systems.

Simultaneous monitoring of flow patterns, and bubble, and plastics micro-particle characteristics in Dissolved Air Flotation (DAF)

Dissolved air flotation (DAF) is an important water treatment process for removing suspended solids. Understanding the characteristic size and spatial distribution of both bubbles and suspended solids, including their hydrodynamics, within flotation tanks is key to optimising flotation performance. In this study, a continuously operating lab scale DAF tank was constructed to simultaneously monitor size distributions and motions of microbubbles (Ø = 67–86 ± 13–19 µm) and spherical polyethylene microplastic particles (Ø = 69.8 ± 5.3 µm) in unbuffered water at circumneutral pH without salt addition and with 0.5 g L−1 sodium chloride (NaCl) added. Microplastic particles were used for the first time in such a setup. Particle tracking showed different flow regimes in the separation zone, with short-circuiting flow paths varying at different flow rates. Within the range of flowrates employed, the bubble bed that formed was not prominent enough to promote stratified flow. The addition of NaCl greatly reduced microplastic particle counts within the separation zone during flotation. This new multi-factorial approach provides critical insights into the variations in DAF performance.

Common Issues in Aeration System Choice for Flotation Wastewater Treatment

Flotation wastewater treatment is widely used in various treatment systems. The choice of aeration system plays a considerable role in the development of highly efficient flotation tanks. The objective of this work is to point out factors that influence the choice of flotator type, and to offer recommendations based on literature review and data analysis. In this paper, the various types of aeration systems used in flotation tanks are considered: mechanical, pneumatic, pneumohydraulic and ejection systems as well as dissolved air flotation and electroflotation systems. Their main advantages and disadvantages are pointed out. The specific features of flotation tank constructions are considered. The factors that influence the choice of aeration system such as the parameters of wastewater (pH, conductivity, temperature), requirements for the quality of treated water, reliability and simplicity of maintenance, capital and operating costs are defined. The peculiarities of various aeration system applications in different conditions are revealed. A comparison of the energy consumption of the considered systems of aeration is presented. In conclusion, practical recommendations for the choice of aeration system depending on various factors are offered.

Effect of Retrofit Design Modifications on the Macroturbulence of a Three-Phase Flotation Tank-Flow Characterization Using Positron Emission Particle Tracking (PEPT).

Turbulence in stirred tank flotation tanks impacts the bulk transport of particles and has an important role in particle-bubble collisions. These collisions are necessary for attachment, which is the main physicochemical mechanism enabling the separation of valuable minerals from ore in froth flotation. Modifications to the turbulence profile in a flotation tank, therefore, can result in improvements in flotation performance. This work characterized the effect of two retrofit design modifications, a stator system and a horizontal baffle, on the particle dynamics of a laboratory-scale flotation tank. The flow profiles, residence time distributions, and macroturbulent kinetic energy distributions were derived from positron emission particle tracking (PEPT) measurements of tracer particles representing valuable (hydrophobic) mineral particles in flotation. The results show that the use of both retrofit design modifications together improves recovery by increasing the rise velocity of valuable particles and decreasing turbulent kinetic energy in the quiescent zone and at the pulp-froth interface.

Microplastics in wastewater treatment plants: Sources, properties, removal efficiency, removal mechanisms, and interactions with pollutants.

Since wastewater treatment plants (WWTPs) cannot completely remove microplastics (MPs) from wastewater, WWTPs are responsible for the release of millions of MPs into the environment even in 1 day. Therefore, knowing the sources, properties, removal efficiencies and removal mechanisms of MPs in WWTPs is of great importance for the management of MPs. In this paper, firstly the sources of MPs in WWTPs and the quantities and properties (polymer type, shape, size, and color) of MPs in influents, effluents, and sludges of WWTPs are presented. Following this, the MP removal efficiency of different treatment units (primary settling, flotation, biological treatment, secondary settling, filtration-based treatment technologies, and coagulation) in WWTPs is discussed. In the next section, details about MP removal mechanisms in critical treatment units (settling and flotation tanks, bioreactors, sand filters, membrane filters, and coagulation units) in WWTPs are given. In the last section, the mechanisms and factors that are effective in adsorbing organic-inorganic pollutants in wastewater to MPs are presented. Finally, the current situation and research gap in these areas are identified and suggestions are provided for topics that need further research in the future.

A methodology to implement a closed-loop feedback-feedforward level control in a laboratory-scale flotation bank using peristaltic pumps

This paper describes the implementation of a level control strategy in a laboratory-scale flotation system. The laboratory-scale system consists of a bank of three flotation tanks connected in series, which mimics a flotation system found in mineral processing plants. Besides the classical feedback control strategy, we have also included a feedforward strategy to better account for process disturbances. Results revealed that the level control performance significantly improves when a feedforward strategy is considered.This methodology uses peristaltic pumps for level control, which has not been extensively documented even though: (1) peristaltic pumps are commonly used in laboratory-scale systems, and (2) the control implementation is not as straightforward as those control strategies that use valves. Therefore, we believe that this paper, which describes a proven methodology that has been validated in an experimental system, can be a useful reference for many researchers in the field.•Preparation of reagents to ensure that the froth stability of the froth layer is representative of an industrial flotation froth.•Calibration of instruments – convert the electrical signal from PLCs to engineering units.•Tuning PI parameters using SIMC rules by performing step-changes in each flotation cell.

Reduction of TSS, COD, Oil and Fat in Palm Oil Mill Waste Using Dissolved Air Flotation Method

This study aims to determine the effect of variations in pressure and contact time of wastewater with air to decrease the parameters of TSS, COD, and oils and fats contained in palm oil wastewater. This study uses a series of Dissolved Air Flotation (DAF) process units with the addition of Poly Aluminum Chloride (PAC) coagulant. This research begins with the manufacture of a series of DAF tanks and flotation tanks. Waste flow is carried out in batches and the air is flowed upflow through the bottom hole of the DAF tank. The pressure variables used in decreasing the parameters of TSS, COD, and oil and fat are absolute 2; absolute 2.5; and absolute 3 atm. The contact time variables for decreasing TSS, COD, and oil and fat parameters were 15, 30, 45, 60, and 75 minutes. The results showed a decrease in each of the tested parameters. The effective pressure to reduce the value of the TSS parameter is the absolute pressure of 3 atm and the absolute pressure of oil and grease is 2.5 atm. While the effective pressure to reduce the value of the COD parameter is an absolute pressure of 3 atm. The best contact time between air and wastewater to set aside the values of the TSS, COD, and oil-fat parameters was 75 minutes.

ECONOMIC DESIGN OF PIPE-NOZZLE DISCHARGE LINES DELIVERING FREE JETS

The present study focuses on finding an economic design of nozzles used in water discharge lines. An analytical solution is reached for computing the economic pipe-nozzle diameter ratio achieving the minimum pipe cost using the derivative method. The derived equation shows that at a particular pipe-nozzle diameter ratio, the pipe cost CP is minimum. However, this is evident from the worked illustrative example. On a comparison basis between this equation and the conventional one, the derived equation shows a satisfactory reduction in the pipe cost, which may reach 56.7%. It is of great interest to recognize that, by increasing the relative distance to 400, a reduction in pipe cost of 231 % associated with an increase in the power of the jet by 41.5 %, are verified. Also, the derived equation achieves a reduction in pipe cost ranging from 34 to 39.7 % depending on the frictional effects in the approach pipe. The study reflects the reliability of the derived equation in computing the economic pipe-nozzle diameter ratio used in discharge lines delivering free jets. However, there are many engineering applications of water jet nozzles used in; water filters, flotation tanks, sedimentation tanks, water storage tanks, trickling filters, and other units of water and wastewater systems.

Определение оптимальной конструкции очистного аппарата сточных вод после гидроабразивной резки

The analysis of flotation tanks and the composition of waste water after hydroabrasive cutting has been carried out. The most optimal design of the treatment unit for waste water treatment of a hydroabrasive machine was been determined. The results of studies aimed at determining the main parameters and the principle of operation of a waste water treatment plant for waste water treatment after the hydroabrasive cutting are presented.

Brain volumetric changes after sensory isolation: single case experimental design

This study aimed to investigate the cerebral volumetric changes measurable by brain magnetic resonance imaging, as well as the different physiological variables documented through neurobiofeedback equipment, before and after 30 serial sessions of guided meditations in a sensory isolation tank. A pilot test was carried out, with a single subject, and it was concluded that serial sessions of meditations in flotation tanks changed the brain structure, triggered the relaxation response, generating greater physical, psychological and mental well-being for the research participant.

Analysis of the Influencing Factors on Oil Removal Efficiency in Large-Scale Flotation Tanks: Experimental Observation and Numerical Simulation

A modified computational fluid dynamic (CFD) model has been developed to obtain oil removal efficiency for oily wastewater treatment in large-scale flotation tanks. According to the investigation of oil droplet/bubble interactions in a flotation tank, a modified Bloom–Heindel model is used to calculate the collision and attachment efficiencies between oil droplets and bubbles. Effects of the gas flow rate, oil diameter and oil concentration on oil removal efficiency of flotation tank were analyzed experimentally. The application scope of this modified CFD model is evaluated using experimental results. In addition, the comparison between the existing model and the modified model demonstrates that this modified CFD model can make a good prediction for the separation performance of the flotation tank.

A framework for polydisperse pulp phase modelling in flotation

Froth flotation is one of the most widely-used mineral processing operations. The pulp zone in flotation tanks is polydisperse in general and serves as a medium for the interaction between the solid particles and the gas bubbles in a liquid continuum, leading to particle–bubble attachment/detachment and bubble coalescence/breakage phenomena. To better predict the hydrodynamics and inform the design of efficient flotation equipment, it is therefore important to accurately model and simulate the evolution of the size distribution of the dispersed phases. This has created an urgent need for a framework that can model the pulp phase in an efficient manner, which is not currently available in the literature. The available software products are not efficient enough to allow for a tractable modelling of industrial-scale flotation cells and in some cases they cannot model the polydispersity of the dispersed phase at all. This work presents an efficient numerical framework for the macroscale simulation of the polydisperse pulp phase in froth flotation in an open-source finite element computational fluid dynamics (CFD) code that provides an efficient solution method using mesh adaptivity and code parallelisation. A (hybrid finite element–control volume) finite element framework for modelling the pulp phase has been presented for the first time in this work. An Eulerian–Eulerian turbulent flow model was implemented in this work including a transport equation for attached and free solid particles. Special care was taken to model the settling velocity of the free solids and the modification of the liquid viscosity due to the presence of these particles. Bubble polydispersity was modelled using the population balance equation (PBE), which was solved using the direct quadrature method of moments (DQMOM). Appropriate functions for bubble coalescence and breakage were chosen in the PBE. Mesh adaptivity was applied to the current problem to produce fully-unstructured anisotropic meshes, which improved the solution efficiency, while all simulations were executed on a multicore architecture. The model was validated for 2D simulations of a bubble column against experimental results available in the literature. After successful validation, the model was applied to the simulation of the pulp phase in a flotation column for monodisperse and polydisperse solids. Polydispersity of the solids was modelled for the first time in this work using three separate solid size classes. A clear dependence of the flotation rate on the particle size was noticed and the monodisperse solids simulations were shown to over-predict the flotation rate. Other than flotation, this open-source framework can be used for the simulation of a variety of polydisperse multiphase flow problems in the process industry.

Weight reduction and possible implications for the rehabilitation of horses with ambulatory difficulties

SummaryEquine musculoskeletal injuries, or other causes of reduced movement, can have a poor prognosis partially due to the secondary complications that may develop during recovery or rehabilitation. These can include supporting limb laminitis due to excessive weightbearing on healthy limbs and also problems associated with ventilation or perfusion due to prolonged recumbency. The risk of these complications is reported to increase with increasing body weight. While many methods have been attempted to reduce load and prevent complications, there is no current standard practice when managing horses with ambulatory difficulties. One critical consideration with load reduction devices is maintaining sufficient mobility to allow for blood flow and the prevention of muscle wasting. One of the most challenging obstacles with any weight reduction method or device is preventing pressure sores/ulcers or other tissue trauma because load is redistributed away from the limbs and onto regions of the body unaccustomed to weightbearing. Reported methods to aid in recovery and rehabilitation include rescue slings, forced recumbency, flotation tanks, water treadmills and aquatic therapy. While these methods have been successful in some horses, significant complications have also been reported. If too much weight is removed, muscle wasting or osteopenia occurs; conversely, if insufficient weight is lifted blood flow is hindered. The optimal load reduction is not known because each individual horse will have different requirements depending on the severity of the injury. The goal would be to restore normal weight distribution on the noninjured limbs, while supporting the weight that would normally be placed on the injured limb.

Effects of internal geometry on hydrodynamics of dissolved air flotation (DAF) tank: An experimental study using particle image velocimetry (PIV)

The hydrodynamics of flotation tanks significantly affect the removal efficiency of dissolved air flotation (DAF) systems. In the present study, for the first time, particle image velocimetry (PIV) was used to provide a fully detailed map of the velocity field in the contact and separation zones of a real scale DAF system under the influence of different internal geometries. The observed flow patterns indicated that flow circulations occur in the upper part of the contact zone, and as the height of the inlet baffle increased, the flow circulations became more intense. Additionally, as the inlet baffle was inclined, the flow inside the contact zone deviated from the plug flow. The outlet baffle contributed to the formation of a large rotational flow in the separation zone, and the shape of the rotational flow was a function of inlet baffles’ height. The range of the measured velocities of microbubbles in this study varied between 0–64 mm/s in the contact zone which was greater than the estimated rising velocities by Stoke’s law (1.37–17.82 mm/s). The velocities of microbubbles were also measured in the separation zone which varied between 0–25 mm/s. For the same internal geometry and flow conditions, the hydrodynamics of the flow without microbubbles (single phase flow) was also investigated. Results showed that the velocity of microbubbles was higher than single-phase flow (varied between 0 and 38 mm/s). Moreover, it appears that the buoyancy of microbubbles enhances the formation of rotational flows inside the separation zone.

Scale-up in froth flotation: A state-of-the-art review

Abstract Froth flotation has been one of the most important and widely used methods to concentrate minerals since its introduction over a hundred years ago. Over the last few decades, in order to process more mineral while reducing capital costs, flotation equipment has become exponentially larger. The increase in tank volume, however, has brought new challenges in the operation and design of industrial flotation tanks. This review analyses the literature on flotation tank scale-up for the first time, contrasting several techniques and approaches used in both historical and state-of-the-art research. The study of flotation scale-up is crucial for the optimisation of industrial plant performance and the maximisation of laboratory-scale research impact. While important advances in our understanding of flotation have been achieved, large flotation tank design and scale-up has, to a large extent, remained in-house know-how of manufacturing companies. This review of the literature relevant to flotation tank scale-up has resulted in a new classification, dividing the scale-up literature into two main areas of study, namely “Kinetic scale-up” and “Machine design scale-up”. This review indicates that current scale-up rules governing the design of flotation tanks focus mainly on pulp zone kinetic parameters and neglect the effects on the froth zone, despite the importance of froth stability and mobility in determining flotation performance. Froth stability and mobility are closely linked to the distance the froth needs to travel, which increases with tank diameter. Although including internal elements, such as launders and crowders, has been the industrial solution for enhancing froth transport and recovery in larger tanks, the design and scale-up of these elements have not been thoroughly studied. Gaps in our knowledge of flotation are discussed in the context of addressing the scale-up problem, considering froth transport and froth stability. Addressing these gaps will pave the way for the design and operation of large flotation tanks of enhanced performance.

A dynamic model for level prediction in aerated tanks

Stirred aerated tanks are a key unit operation in many industries, including froth flotation. Reliable and robust level control is of great importance in maintaining steady operation for successful implementation of higher level optimising control strategies, particularly when such tanks are arranged in series. When changes are made to the rate of aeration, there is a corresponding change in the pulp bubble size and gas holdup (the volume fraction of air in the tank), and consequently the pulp height. Stable operation of flotation tanks must, therefore, include the effect of air rate on pulp height in level control systems, especially if air rate is being actively controlled. In this paper, a model is developed from first principles to link the change in gas holdup with variation in air rate under dynamic conditions, accounting for the variability in gas holdup with height that results from differences in gas compressibility. This is validated experimentally.In order to test the model, experiments were carried out using a 70 L laboratory tank comprising water and reagent systems. For both simple and complex changes in air rate, the model showed good agreement with the experimental results when predicting the change in pulp height at steady state. Under dynamic conditions, the experimental system exhibited a slightly slower response than is predicted by the model; this is likely to be due to the well mixed assumption not being adequately met.This model provides a method to improve the operating stability of aerated tanks through better modelling of the dynamic pulp height changes that result from changes in air flowrate. In flotation tanks, this will enable greater control over froth height, which has been found to affect significantly mass pull, froth stability and flotation performance.

Sensory Isolation in Flotation Tanks: Altered States of Consciousness and Effects on Well-being

A qualitative analysis (The Empirical Phenomenological Psychological method) of interviews involving eight patients (depression, burn-out syndrome, and chronic pain) was carried out in order to obtain knowledge regarding the effects of flotation tank therapy. This knowledge might be helpful for both professionals and potential floaters. The analysis resulted in 21 categories, which were summarized as four themes: (a) experiences during flotation, (b) perceived effects afterwards, (c) technical details, and finally (d) the participants ́ background, motivation, and expectations. Floating was perceived as pleasant. An altered state of consciousness was induced, varying from a milder state including profound relaxation and altered time perception, to more powerful with perceptual changes and profound sensations such as out-o f-body experience s and perinatal experiences.

Curing the sick and creating supermen – How relaxation in flotation tanks is advertised on the Internet

IntroductionFlotation-REST (Restricted Environmental Stimulation Technique) is a complementary and alternative medicine therapy with evidence-based beneficial effects like pain and stress reduction. During flotation-REST a person is lying in a supine position inside a quiet and dark tank, filled with salt water maintained at skin temperature. The water is high in buoyancy, which makes it possible to float comfortably on the back. The method induces deep relaxation through minimization of sensory input. Contemporary scientific findings about beneficial effects resulting from floating have increased the number of private owned floating centers. The aim of this study was to investigate how these centers advertise the benefits of flotation to the public and compare these claims with published scientific evidence. MethodThe Google search engine was used to localize web-sites hosting private floating center entrepreneurs. Described effects resulting from floating on these sites were systematically gathered and analyzed thematically. In addition, advertisements were compared to scientific studies on flotation-REST. ResultsThe analysis resulted in five overarching themes: (1) Physiological changes, (2) Alleviation of medical conditions, (3) Relaxation, (4) Personal growth and enhancement, and (5) Altered states of consciousness. Advertisements seemed to target four different interest groups: the inner explorers; the sick; the supermen; and the stressed out. Various effects of flotation were highlighted for the different groups and some limited scientific evidence identified. ConclusionsAlthough the advertisements described many evidence-based effects resulting from floating, information tended to be exaggerated, could be misleading to consumers, and was not always substantiated by published scientific studies.

An Unusual Death Involving a Sensory Deprivation Tank*

Deaths involving sensory deprivation tanks are very rare. We describe a unique case in which a previously healthy 50-year-old woman apparently died while floating in a sensory deprivation tank at her residence. Autopsy failed to reveal definitive anatomical abnormalities pointing to the cause of death. A thorough scene investigation, full medicolegal autopsy to include toxicological analyses, and a complete investigation into the equipment at the scene, were conducted. Blood toxicologic studies were significant for the presence of ethanol (0.27%) and a mixture of over-the-counter sedating medications and prescription drugs. The cause of death was ruled as acute mixed drug and ethanol toxicity combined with probable environmental hyperthermia; manner was accident. This case report will help the forensic community understand the intended use of flotation tanks, as well as possible risks associated with improper use.

The Hand-Pump Flotation System: A New Method for Archaeobotanical Recovery

At the sites of Acquachiara in Italy, el-Hemmeh in Jordan, and Beisamoun in Israel, archaeobotanical recovery was accomplished using flotation systems powered by hand-pumps, as opposed to non-circulating systems or systems powered by electricity or gasoline. These flotation tanks were simple and inexpensive to construct, easily operated by a single individual, highly durable, and easily transported. The speed of water flow was both ample and could be controlled without difficulty. These systems had the capacity to process samples at a rate sufficient to keep pace with large-scale sampling programs at all three sites. In three case studies, we describe two tanks that recycle water and one that does not, list the parts and procedures necessary to construct a hand-pump system, and detail the results of a recovery test that demonstrates the efficacy of this technique. The type of flotation tank described would be appropriate for a range of research projects with various resource constraints, enabling substantial paleoethnobotanical data collection with only a minimal initial investment of time and money.