Salt effect on gas dispersion in flotation column – Bubble size as a function of turbulent intensity

Filippov, L.O.; Jávor, Zoltán; Piriou, P.; Filippova, I.V.

doi:10.1016/j.mineng.2018.07.017

Cited by 21 publications

(13 citation statements)

References 48 publications

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“…One such event for freshwater at a bulk velocity of 0.8 m s –1 is shown in Figure A–H, where two bubbles of ∼2 mm each coalesces to form a single bubble in ∼16 ms (from time of first bubble–bubble contact to the formation of a single bubble). For gas bubbles to coalescence, contact between two bubbles is required, with bubble collision frequency affecting how often coalescence can occur . The mechanics of bubble coalescence are dependent on several factors: ionic salt species, interfacial tension, and phase viscosities …”

Section: Resultsmentioning

confidence: 99%

“…With the addition of weak monovalent ionic salts, such as NaCl, it has been shown that dissolved ionic species will preferentially approach the interface ,, (Figure ). This is possible due to water molecule anisotropy (water molecule alignment) at the gas–water interface, which polarizes anions and induces temporary dipoles at the interface that do not exist in the bulk continuous phase .…”

Section: Resultsmentioning

confidence: 99%

“…This is possible due to water molecule anisotropy (water molecule alignment) at the gas–water interface, which polarizes anions and induces temporary dipoles at the interface that do not exist in the bulk continuous phase . With NaCl, the induced dipoles in Cl ‑ ions enable preferential adsorption to the gas–water interface over Na + ions , (Figure ), which may cause colliding bubbles to repel instead of coalescing, hence the lack of observable coalescence in saltwater experiments.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Hydrate Growth on Methane Gas Bubbles in the Presence of Salt

Charlton

Aman

et al. 2019

Langmuir

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Methane bubble dispersions in a water column can be observed in both vertical subsea piping as well as subsea gas seepages. Hydrate growth has been shown to occur at the gas−water interface under flowing conditions, yet the majority of the current literature is limited to quiescent systems. Gas hydrate risks in subsea piping have been shown to increase in late life production wells with increased water content and with gas-in-water bubble dispersions. The dissolution of subsea methane seepages into seawater, or methane release into the atmosphere, can be affected by hydrate film growth on rising bubbles. A high-pressure water tunnel (HPWT), was used to generate a turbulent, continuous water flow system representative of a vertical jumper line to study the relationship between bulk methane hydrate growth and bubble size during a production-well restart. The HPWT comprises a flow loop of 19.1 mm inner diameter and 4.9 m length, with a vertical section containing an optical window to enable visualization of the bubble and hydrate flow dynamics via a high-speed, high-resolution video camera. Additional online monitoring includes the differential pressure drop, viscosity, temperature, flow rates, and gas consumption. Experimental conditions were maintained at 275 K and 6.2 MPa during hydrate formation and 298 K and 1.4 MPa during hydrate dissociation. Hydrate growth using freshwater and saltwater (3.5 wt % NaCl) was measured at four flow velocities (0.8, 1.2, 1.6, and 1.9 m s −1 ). The addition of salt is shown in this work to alter the surface properties of bubbles, which introduces changes to bubble dynamics of dispersion and coalescence. Hydrate volume fractions and growth rates in the presence of salt were on average ∼32% lower compared to that in freshwater. This was observed and validated to be due to bubble size and dynamic factors and not due to the 1.5 K thermodynamic inhibition effect of salt. Throughout hydrate growth, methane bubbles in pure freshwater maintained larger diameters (2.4−4.2 mm), whereas the presence of salt promoted fine gas bubble dispersions (0.1−0.7 mm), increasing gas−water interfacial area. While gas bubble coalescence was observed in all freshwater experiments, the addition of salt limited coalescence between gas bubbles and reduced bubble size. Consequently, earlier formation of solid hydrate shells in saltwater produced early masstransfer barriers reducing hydrate growth rates. While primarily directed toward flow assurance, the observed relationship between hydrates, bubble size, and saltwater also applies to broader research fields in subsea gas seepages and naturally occurring hydrates.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Hydrate Growth on Methane Gas Bubbles in the Presence of Salt

Charlton

Aman

et al. 2019

Langmuir

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“…Bubble columns have been applied widely in the fields of biochemical, pharmacy, water treatment, and gas absorption, 1–7 which have many characteristics including simple structure, easy operation, good performance of heat and mass transfer, as well as low operation cost 8–10 . In addition, as a typical mineral separation process based on bubble–particle interaction, flotation is often carried out in the bubble column 11–14 . However, bubbles in the common column are often at millimeter scale, which results in the low gas holdup and interfacial area 15 .…”

Section: Introductionmentioning

confidence: 99%

The effect of inorganic salt on multiphase flow characteristics in a microbubble column: A focus on the ionic strength

Jia

Shen

et al. 2021

Asia-Pacific J Chem Eng

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With enormous interfacial area for particle collection, microbubbles exhibit great application prospect in the mineral flotation. Under certain ionic strength, microbubbles can be produced continuously in the microbubble column without extra reagent addition. In this work, multiphase flow characteristics (Sauter mean diameter, bubble size distribution, gas holdup & interfacial area) were studied systematically with variables including the salt type, salt concentration, and operating conditions. Based on mathematical model, critical coalescence concentration was determined for each investigated salt. According to experimental results, a mathematical correlation was established between the Sauter mean diameter and ionic strength. For the formation of microbubble system, the lowest ionic strength was approximately 0.5 mol/L. Multiphase flow characteristics in the microbubble column depended highly on the ionic strength. The interfacial area and gas holdup increased by 38 times and more than 3 times respectively, with the ionic strength of Al2(SO4)3 rising from 0 to 1.5 mol/L. The critical coalescence concentration ranged from 0.037 mol/L (Al2(SO4)3) to 0.517 mol/L (NaCl), which correlated with the ionic strength of each salt.

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“…It needs an in-depth study of technical and economic feasibility [14], being the flotation an adequate technique for the concentration and recovery of minerals from ores and waste. The flotation in column also represents an appropriate option for the recovery and or concentration of minerals, where the model studied is related to a stable state behavior, taking in account variables such as dynamic mass balance, type of pulp, markers, bubble distribution and flux, bubble size, cations effect, and bubble coalescence, among others [15][16][17].In this context, the principal aim of this work is to recover silica by column flotation, using the tailings form the "Dos Carlos" dam. This proposal offers significant advantages since it reuses a material considered waste.…”

mentioning

confidence: 99%

Assessment of Silica Recovery from Metallurgical Mining Waste, by Means of Column Flotation

Salinas‐Rodríguez

Flores-Badillo

Hernández-Ávila

et al. 2020

Metals

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The generation of mining waste commonly led to the use of spaces for its disposal. Challenges like mitigating the damage to surrounding communities have promoted the need to reuse, recycle and/or reduce their generation. Besides, these residues may become a source of materials, which are capable of being recovered and reused in several industries, minimizing the environmental impact. In the mining region of Pachuca, Mexico, waste from the mining industry have been generated for more than 100 years, which have a high SiO2 content that can be recovered for various industrial applications. This work aims to recover silica from a material of the Dos Carlos dam. A columnar system composed of two-stage of cleaning was used, considering a JLT (surface liquid rate) value of 0.45 and 0.68 cm/s, respectively; while the Jg (surface gas rate) value was 0.30 cm/s for both stages. Similar bubble sizes in the range of Jg 0.10 to 0.30 cm/s, with values between 0.14 and 0.16 cm in the first stage, and 0.05 to 0.06 cm in the second one. This provided a recovery of 75.10% for all the allotropic phases of silica (quartz, trydimite, and cristobalite) leaving a concentration of 24.90% of a feldspathic phase (orthoclase), as flotation tails.

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Salt effect on gas dispersion in flotation column – Bubble size as a function of turbulent intensity

Cited by 21 publications

References 48 publications

Hydrate Growth on Methane Gas Bubbles in the Presence of Salt

Hydrate Growth on Methane Gas Bubbles in the Presence of Salt

The effect of inorganic salt on multiphase flow characteristics in a microbubble column: A focus on the ionic strength

Assessment of Silica Recovery from Metallurgical Mining Waste, by Means of Column Flotation

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