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1

Artificial neural network (ANN) modelling to estimate bubble size from macroscopic image and object features

Vinnett Luis, León Roberto, Mesa Diego

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 5

art. no. 185759

EN

Bubble size measurements in aerated systems such as froth flotation cells are critical for controlling gas dispersion. Commonly, bubbles are measured by obtaining representative photographs, which are then analyzed using segmentation and identification software tools. Recent developments have focused on enhancing these segmentation tools. However, the main challenges around complex bubble cluster segmentation remain unresolved, while the tools to tackle these challenges have become increasingly complex and computationally expensive. In this work, we propose an alternative solution, circumventing the need for image segmentation and bubble identification. An Artificial Neural Network (ANN) was trained to estimate the Sauter mean bubble size (D32) based on macroscopic image features obtained with simple and inexpensive image analysis. The results showed excellent prediction accuracy, with a correlation coefficient, R, over 0.998 in the testing stage, and without bias in its error distribution. This machine learning tool paves the way for robust and fast estimation of bubble size under complex bubble images, without the need of image segmentation.

2

A discussion on the limitations of image analysis for determining bubble size in industrial flotation when using algorithms successfully tested from idealized images

Vinnett Luis

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 5

art. no. 174474

EN

This paper evaluates the capacity of an automated algorithm to detect bubbles and estimate bubble size (Sauter mean diameter, D32) from images recorded in industrial flotation machines. The algorithm is previously calibrated from laboratory images. The D32 results are compared with semi-automated estimations, which are used as "ground truth". Although the automated algorithm is reliable to estimate bubble size at laboratory scale, a significant bias is observed from industrial images for D32 >3.0-4.0 mm. This uncertainty is caused by the presence of small and large bubbles in the same population, with large bubbles forming complex clusters and being observed incomplete, limited by the region of interest. Flotation columns are more prone to this condition, which hinders the estimation of Sauter diameters. The results show the need for bubble size databases that include industrial images. As several image processing tools are currently available, software calibration from ideal bubble images (synthetic or from laboratory rigs) will mostly lead to biased D32 estimations in industrial flotation machines.

3

Critical coalescence concentration (CCC) of various surfactants used as flotation reagents in mineral

Szyszka Danuta

Mining Science

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2022

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Vol. 29

221--232

EN

The role of flotation frothing agents in the flotation process is generally known, especially due to the size of bubbles and the stability of the foam formed. In recent years, a number of new reagents have been introduced. The purpose of this article is to present a comprehensive database containing the characteristics of surfactant families discussed using the parameter of the so called the Critical Coalescence Concentration (CCC). This article presents an analysis of the experimental data set by the author and the experimental data published in the literature.

4

Relative wettability measurement of porous diffuser and its impact on the generated bubble size

Al-Yaqoobi Atheer M.G., Zimmerman William B.

Chemical and Process Engineering

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2022

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Vol. 43, nr 1

45-–55

EN

Controlling the bubble size is a major concern in enhancing transport performance in gas-liquid systems. The role of wettability of diffuser surface on bubble size is the subject of the current work. The study inspects the contact angle of a set of liquids on HP ceramic diffusers using the Washburn method. The results demonstrate that organic liquids like toluene, methanol–water (1:1 v/v), ethanol– water (1:1 v/v) and decane have small contact angles of 12.9, 37.5, 24.4 and 22.5 respectively. Water has a lower wettability than the organic compounds where the contact angle was about 67.4. The effect of wettability of the bubble size is investigated by measuring the size of air bubble produced using the same diffuser material. The results of bubble size measurement demonstrates that with liquids of small contact angle, i.e. good wetting properties, small bubble sizes are produced in comparison with liquids with a higher contact angle. The study demonstrates the viability of Washburn method in characterization of wettability of porous diffuser, which was verified by measuring the bubble size produced. A high reduction in bubble size can be obtained by a carefully chosen diffuser material that provides better wettability.

5

Investigation of the frother effect in two and three phases systems on bubble size, surface tension, recovery and grade in chalcopyrite flotation

Ceylan Adnan, Bulut Gülay

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 6

23--35

EN

In this study, the effect of frother was investigated in two and three phases in the systems of the flotation. While the two-phase system consisted of liquid and gas, the three-phase systems contained a chalcopyrite ore. The study of three-phase systems was performed with the ore on a laboratory and plant scale. Effect of the amount and type of the frothers, their mixtures, and pH were examined depending on the bubble size, grade of the concentrate, and the recovery of chalcopyrite flotation. The results showed that as the amount of frothers increased, there was a reduction in the bubble size in all experiments. Additionally, the frother mixtures gave a positive effect on the chalcopyrite flotation. One of the most important purposes of flotation frothers shrinks the air bubble. As can be understood from the tests this time reduction of the frothers bubble size has a positive effect on the flotation. Likewise, it increases the foam stable value. It is observed from this study that increasing the amount of frothers decreases the surface tension and bubble size at different pH.

6

Froth stabilisation using nanoparticles in mineral flotation

Cilek E. C., Uysal K.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

878--889

EN

In this study, three kinds of nanoparticles (SiO2, Fe2O3, and Al2O3) were used in the flotation of a sulphide ore to investigate the effects of nanoparticles on the froth stability and the flotation performance. The dynamic froth stability factor and the maximum froth depth were measured by using a non-overflowing flotation cell under various flotation conditions. The results were also related to the separation selectivity and efficiency of the flotation. The experimental results showed that the dynamic froth stability factor and the maximum froth depth can be increased 1.2-2 fold by using the Al2O3 nanoparticles. These increments led to significant improve in the froth recovery. In terms of the froth stability and the flotation performance, the Al2O3 nanomaterial was the best, followed by Fe2O3 and SiO2. In addition, the flotation recovery increased from 83 to 91%, and the grade of the concentrate increased from 44 to 60% by using the Al2O3 nanoparticles.

7

Zastosowanie autokorelacji do określania prędkości pęcherzyków gazu na podstawie zdjęć z podwójną ekspozycją

Kuncewicz C., Stelmach J.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 1

63-64

PL

W pracy zbadano możliwość określania wielkości pęcherzyków w układzie dwufazowym ciecz - gaz przez analizę zdjęć uzyskanych z podwójną ekspozycją. Stosując metodę autokorelacji oraz znając odstęp czasowy i przesunięcie na środka pęcherzyka na ekranie można było na tej podstawie określić prędkość i kierunek poruszania się pęcherzyka. Wykonane badania doświadczalne dla napowietrzania w mieszalniku potwierdziły możliwość zastosowania tej metody w praktyce wskazując jednocześnie no konieczność lepszego dopracowania proponowanej metody.

EN

In the study a possibility to determine gas bubble size in the two-phase gas - liquid system was investigated via analysis of double exposure photo- graphs. Based on the autocorrelation method and knowing the time interval ; and displacement from the middle of bubble, it was possible to determine the velocity and direction of bubble movement. The experimental investigations performed for aeration in the mixer confirmed a possibility to apply this method in practice, indicating simultaneously the necessity of its further elaboration.

8

Rozmiary pęcherzyków w początkowej fazie samozasysania

Stelmach J.

Inżynieria i Aparatura Chemiczna

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2006

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Nr 6s

225-227

EN

Gas bubble size was determined by a photographic method on the level of suspension of a self-aspirating disk impeller in the initial phase of self-aspiration. The size of gas bubbles depends on the impeller diameter, height of the liquid over the impeller and rotational frequency of the impeller, i.e. the modified Froude number. The sizes increase with an increase of the Froude number.

9

Bubble size distribution of foam

Den Engelsen C. W., Isarin J. C., Gooijer H., Warmoeskerken M. M. C. G., Groot Wassink J. G.

Autex Research Journal

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2002

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Vol. 2, no. 1

14--27

EN

A procedure based upon image analysis has been adopted to study the influence of several physical parameters on bubble size in foam. A procedure has been described to account for the distribution of bubble size. Foam was generated in a rotor-stator mixer. In the present research, the nature of the surfactant, liquid viscosity, solid phase content, and rotational speed of the mixer were varied. All parameters were found to influence the bubble size and its distribution to a certain extent. These effects were qualified experimentally.