Publications
96 results found
Zhang H, An S, Brito-Parada PR, et al., 2024, Investigation into three-dimensional dry foam modelling using the boundary integral method, Journal of Computational Physics, Vol: 499, ISSN: 0021-9991
Understanding foam rheology relies on predictions of the foam structure and physical quantities associated with foam dynamics. In this work, we explore the modelling of dry foam dynamics using the boundary integral method, which can be used to predict the behaviour of dry foam in bulk or in confined geometries. The resultant equation for dry foam shows that the movement of foam films or lamellae is governed by the film curvature and the normal stress that the wall imposes on the fluid phase in bubbles and is characterized by three distinct motion modes: the background flow, the imposed flow due to the deformation of wall and the relaxation process of films. The singular integrals involved in the model are handled using a combined method of singularity subtraction and nonsingular contour integral. To demonstrate the validity of the method in potential applications, we consider two scenarios, for foam in bulk and in confined geometries, respectively. Dynamic foam motion is tracked using the model. The results show that the dry foam model has potentials applied in a variety of applications, such as foam flow in microfluidic devices and porous media.
Neethling SJ, Mesa D, Brito-Parada PR, 2024, An improved model for predicting froth recovery, Minerals Engineering, Vol: 205, ISSN: 0892-6875
In froth flotation, froth recovery is a key factor as it quantifies the effect that the froth has on the overall cell recovery. Froth recovery is affected by a number of variables, including froth stability, particle size and density, and the operating conditions of the flotation cell. Despite its importance, modelling froth recovery is challenging due to the large number of competing effects involved. In this paper, we present a model for froth recovery that takes into account the effects of detachment and subsequent transport of particles. The model is phenomenological and is derived from a set of coupled partial differential equations used to describe both liquid and particle motion within a froth. An analytical algebraic solution is obtained for the froth recovery by making a number of assumptions, which are discussed and justified in the paper. This model is related to a previous model produced by the authors, in which froth recovery was described in terms of a constant particle detachment fraction. Conversely, this enhanced model includes an improved description for particle detachment behaviour during coalescence events, allowing for a variable particle detachment fraction. The key parameters in the model are two dimensionless groups. The first group combines the particle settling velocity, the air addition rate and froth stability parameters such as air recovery and the change in bubble size over the froth, while the second key dimensionless group is the ratio of the surface loading on the incoming bubbles to the maximum surface loading. This model is compared to experimental results and is shown to accurately describe the evolution of the froth recovery behaviour down a bank of cells in response to the decreasing froth stability.
Zhang H, Torres-Ulloa C, An S, et al., 2024, A comparative study of a viscous froth lens in two and three dimensions, Physics of Fluids, Vol: 36, ISSN: 1070-6631
The two-dimensional (2D) viscous froth model was initially designed to capture the dynamic behavior of dry foams within a Hele–Shaw cell, characterized by two parallel covering plates separated by a small gap. However, due to its inherent 2D nature, this model does not explicitly account for the dimension across the gap. To address this limitation, we have opted for a three-dimensional (3D) version of the viscous froth model. In this 3D model, the dynamic effect is introduced through the motion of the surface Plateau borders, while the configurations of films in bulk are determined via surface energy minimization subject to specified bubble volumes and surface Plateau border locations. We use this 3D model to simulate the motion of a viscous froth lens within a straight channel. The steady states of the viscous froth lens in 3D are primarily influenced by the driving velocity-to-gap size ratio, particularly at relatively small values of this ratio. By contrast, as the ratio becomes relatively large, the gap size begins to play a significant role in influencing the behavior of the viscous froth lens in 3D. Differences are observed in the steady-state configurations of the viscous froth lens in 3D when compared to those in 2D. However, the behavior of the viscous froth lens in 2D can be better aligned with the results in 3D by treating the drag coefficient required in the 2D viscous froth model as a fitting parameter. A further quantitative analysis indicates that the drag coefficient needed in the 2D viscous froth model may not serve as a uniform parameter for the entire foam structure. Instead, it may depend on the specific location along the evolving foam films over time.
Chen P, Brito-Parada PR, Song S, et al., 2023, Efficient recovery of gold from low concentration Au(S<inf>2</inf>O<inf>3</inf>)<inf>2</inf><sup>3–</sup> solution by fabricating Ag/MoS<inf>2</inf> Ohmic contact, Applied Surface Science, Vol: 639, ISSN: 0169-4332
The surface decoration of precious metal particles is one of the most effective strategies for improving the photocatalytic activity of semiconductors. In this work, a MoS2-based Ohmic contact was fabricated by depositing Ag nanoparticles on the surface of MoS2 nanosheets (MoS2 NSs) to enhance the photoreduction of Au(Ⅰ) from a low concentration Au(S2O3)23– solution. After the fabrication of Ohmic contact, more efficient interface charge transfer can be achieved under the drive of built-in electric field. As a result, the photogenerated singlet excitons in MoS2 NSs are readily dissociated into free charges with the electrons drifting to Ag NPs, leading to a higher electron concentration on the surface of Ag/MoS2 NSs. The gold recovery of Ag/MoS2 NSs-4.15% reaches up to 96.67% for the low concentration Au(S2O3)23– solution, which is about 3.9 times higher than that of pristine MoS2 NSs (24.82%). The results of this work are encouraging for further development in the surface science of photocatalysis and demonstrate a pathway for efficient gold recovery via photoreduction.
Perin R, Cole K, van Heerden MR, et al., 2023, On the Ability of Positron Emission Particle Tracking (PEPT) to Track Turbulent Flow Paths with Monte Carlo Simulations in GATE, APPLIED SCIENCES-BASEL, Vol: 13
Cole K, Mesa D, van Heerden M, et al., 2023, Effect of Retrofit Design Modifications on the Macroturbulence of a Three-Phase Flotation Tank-Flow Characterization Using Positron Emission Particle Tracking (PEPT), INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 62, Pages: 7580-7591, ISSN: 0888-5885
Deveci M, Varouchakis EA, Brito-Parada PR, et al., 2023, Evaluation of risks impeding sustainable mining using Fermatean fuzzy score function based SWARA method, Applied Soft Computing, Vol: 139, Pages: 1-16, ISSN: 1568-4946
Sustainability in the mining and raw materials sector is a key target in the EU Green deal agenda. The aim of this work is to determine the degree of importance of risks that may impede sustainable mining, considering UN Sustainable Development Goals (SDGs) indicators and EU initiatives, taking as a case study the mining sector in Greece. A total of 49 risks for sustainable mining, under six categories, were identified by means of expert consultation and review of the literature. The identification and prioritization of potential risks can provide a pathway towards sustainable mining operations. The risks factors weighting is enhanced using a new Fermatean fuzzy score function with Stepwise Weight Assessment Ratio Analysis (SWARA). The proposed model is a powerful tool to handle the uncertainties and inaccuracies in the information regarding the weights of the risks. The main research findings indicate that the most important risks for sustainable mining in Greece are irresponsible mining, the lack of license to operate, and poor environmental monitoring, which are directly connected to the aim and scope of SDG12: responsible consumption and production. In addition, according to the results the category with the highest risk for sustainable mining is the one of “Risk to Environment”. A complete list of risks and risk categories, and their ranking is presented and discussed creating a priority of actions in the framework of European and international initiatives to set a road map to sustainable mining. This work provides a benchmark for future studies, with the aim of providing a tool for evaluating and ranking global risk factors that may affect sustainable mining development.
Quintanilla P, Navia D, Neethling SJ, et al., 2023, Economic model predictive control for a rougher froth flotation cell using physics-based models, Minerals Engineering, Vol: 196, Pages: 1-16, ISSN: 0892-6875
The development of an economic model predictive control (E-MPC) strategy is presented. The strategy uses a novel dynamic flotation model that incorporates the physics of the froth phase in a flotation cell. The dynamic model was previously calibrated and validated using experimental data.Sensitivity analyses were conducted to select a suitable objective function that accounted for both process economics and control variable sensitivities. While the ultimate goal of a rougher flotation cell is to maximise the metallurgical recovery at a steady state for a specified minimum grade, it was evident that the incorporation of air recovery dynamics (which can be measured in real-time) and concentrate grade dynamics (calculated through first-principle models) led to the best results. The addition of a dynamic variable that can be easily measured online, i.e. air recovery, offers great potential to improve plant performance in existing froth flotation systems. Furthermore, a minimum concentrate grade was imposed in the E-MPC strategy. This acts as an economic constraint as it allows the metallurgical recovery to be optimised while ensuring that concentrate grade requirements are met.The dynamic optimisation problem for the E-MPC strategy was discretised using orthogonal collocations, and was implemented in Matlab using automatic differentiation via CasADi. Two typical manipulated variables were considered: air flowrate and pulp height setpoints. Based on laboratory-scale data, the implementation of the E-MPC strategy resulted in improvements ranging from +8 to +22 % in metallurgical recovery, while maintaining the specified grade. This is therefore an encouraging control strategy to explore in larger flotation systems.
Alonzo D, Tabelin CB, Dalona IM, et al., 2023, Bio+mine project: empowering the community to develop a site-specific system for the rehabilitation of a legacy mine, International Journal of Qualitative Methods, Vol: 22, Pages: 1-8, ISSN: 1609-4069
The rehabilitation of legacy mines continues to be a big challenge because of the difficulties in returning them to safe and stable conditions and ensuring that the mined-out areas become productive to support the economic activity of the host community. Previous efforts are often focused on purely technical and environmental aspects, leading to resistance from the local community due to their exclusion from the rehabilitation process. To address the issues associated with legacy mines and lack of participation of the community, we have developed a project, Biodiversity Positive Mining For The Net Zero Challenge (Bio + Mine), focusing on the abandoned Sto. Niño copper mine (Benguet, Philippines). The mine was closed in 1982 without a plan involving local stakeholders and leaving a significant ongoing negative legacy. Using the social-ecological-technological system framework, we will explore the intersections of the structure and functions of socio-economicdemographic, ecological, and technological data useful in devising a more inclusive mitigation strategy for the reconstruction of the supporting ecosystem. We aim to develop a site-specific system, underpinned by the local community's knowledge and practices, that can be a model for wider implementation in other legacy and active mines worldwide.
Quintanilla P, Navia D, Moreno F, et al., 2023, A methodology to implement a closed-loop feedback-feedforward level control in a laboratory-scale flotation bank using peristaltic pumps, MethodsX, Vol: 10, Pages: 1-15, ISSN: 2215-0161
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.
Zhang H, Brito-Parada PR, Neethling SJ, et al., 2022, Yield stress of foam flow in porous media: The effect of bubble trapping, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol: 655, Pages: 1-12, ISSN: 0927-7757
Foam behaves as a yield-stress fluid as it flows in a porous medium. Quasi-static analysis suggests that the yield stress arises from the non-smooth motion of foam films, denoted as lamellae, in pores. In order to study the effect of trapped lamellae on the motion of a moving lamella and consequently on the yield stress of foam, we conduct numerical simulations in the quasi-static limit. We propose a new method utilizing the surface energy minimization algorithm, which explicitly considers the connectivity of pores in a porous medium. We consider two different shapes of pore and vary the number of nearby trapped lamellae to investigate the effects of bubble trapping on the non-smooth and the smooth motion of a single lamella passing through a pore, respectively. We find that the trapped lamellae lead to the increased volume-averaged pressure drop and thus the increased yield stress. Notably, the motion of a lamella through a pore with rounded corners in the pore body becomes non-smooth, due to the presence of trapped lamellae. The results contribute to a better understanding of the yield stress of foam in porous media.
Deveci M, Brito-Parada PR, Pamucar D, et al., 2022, Rough sets based Ordinal Priority Approach to evaluate sustainable development goals (SDGs) for sustainable mining, Resources Policy, Vol: 79, Pages: 1-14, ISSN: 0301-4207
The Sustainable Development Goals (SDGs) have been adopted by countries and companies, including mining companies around the world. The aim of this study is to investigate the degree of importance of the seventeen sustainable development goals (SDGs) on sustainable mining using a rough sets based decision making approach. This novel approach consists of three consecutive stages, namely a questionnaire (survey), data analyses, and SDGs classification. Firstly, a survey is conducted to receive a response from internationally experts across different countries. Each participant is asked to evaluate the importance of each SDG. Secondly, the analyses are carried out to make a distinction among groups of participants who respond similarly and discover viewpoints from the industry, academia, and non-governmental organizations. Finally, the degree of importance of each SDG for sustainable mining is found using a novel decision making approach including Ordinal Priority Approach (OPA) based on rough sets. The survey of the results indicated that for all the participants of the survey, independently of their background, the most important SDG for sustainable mining was “SDG8: Decent work and economic growth”, while the one perceived as the least important was “SDG14: Life below water”. The main objective of SDG8 is to promote economic growth through job opportunities and decent work for all. This in turn leads to a more sustainable, long-term economic growth. While all SDGs play an important role, the proposed rough sets based decision making method provided a rational and objective evaluation performance of their perceived priority in the mining sector.
Sitorus F, Brito-Parada PR, 2022, The selection of renewable energy technologies using a hybrid subjective and objective multiple criteria decision making method, Expert Systems with Applications, Vol: 206, Pages: 1-18, ISSN: 0957-4174
The use of renewable energy technologies is a key factor for sustainable development but their selection from several alternatives is a difficult task that relies on the careful assessment of relevant criteria. While Multiple Criteria Decision Making (MCDM) methods have been used successfully in various renewable energy technology selection problems, the decision process becomes more challenging when preferential judgements are made on the basis of non-homogenous and imprecise input data, and when there is uncertainty due to disparities among decision makers. This paper presents a hybrid MCDM method capable of overcoming these problems by taking into account quantitative and qualitative data under a probabilistic environment in the context of group decision making. In this method, qualitative data is fuzzified and used along with quantitative data to develop a hybrid model. A coefficient factor allows decision makers to vary the weight of each quantitative model so that the resultant criteria weights and overall alternatives’ scores consider both subjective considerations and objective information. An example is presented to showcase the usability of the method developed for ranking and evaluating renewable energy technologies in the mining industry. In addition, the impact of different coefficient factors on the final results was assessed by means of sensitivity analysis. The results indicate that the method developed is able to minimise the loss of valuable objective information, caused by the subjective bias of qualitative weights during the evaluations, by adjusting the coefficient factors of the hybrid model during the calculations.
Wang J, Ray K, Brito-Parada P, et al., 2022, A Bayesian approach for the modelling of material stocks and flows with incomplete data, ArXiv
Material Flow Analysis (MFA) is used to quantify and understand the lifecycles of materials from production to end of use, which enables environmental,social and economic impacts and interventions. MFA is challenging as availabledata is often limited and uncertain, giving rise to an underdetermined systemwith an infinite number of solutions when attempting to calculate the values ofall stocks and flows in the system. Bayesian statistics is an effective way toaddress these challenges as it rigorously quantifies uncertainty in the dataand propagates it in a system flow model to provide the probabilitiesassociated with model solutions. Furthermore, the Bayesian approach provides anatural way to incorporate useful domain knowledge about the system through theelicitation of the prior distribution. This paper presents a novel Bayesian approach to MFA. We propose a mass basedframework that directly models the flow and change in stock variables in thesystem, including systems with simultaneous presence of stocks anddisaggregation of processes. The proposed approach is demonstrated on a globalaluminium cycle, under a scenario where there is a shortage of data, coupledwith weakly informative priors that only require basic information on flows andchange in stocks. Bayesian model checking helps to identify inconsistencies inthe data, and the posterior distribution is used to identify the variables inthe system with the most uncertainty, which can aid data collection. Wenumerically investigate the properties of our method in simulations, and showthat in limited data settings, the elicitation of an informative prior cangreatly improve the performance of Bayesian methods, including for bothestimation accuracy and uncertainty quantification.
Mesa D, van Heerden M, Cole K, et al., 2022, Hydrodynamics in a three-phase flotation system - fluid following with a new hydrogel tracer for Positron Emission Particle Tracking (PEPT), Chemical Engineering Science, Vol: 260, Pages: 1-11, ISSN: 0009-2509
Understanding the hydrodynamics of three-phase stirred tanks, such as froth flotation cells, is paramount for the characterisation of turbulence, stability and performance. Although positron emission particle tracking (PEPT) is known for its effectiveness in measuring the hydrodynamics of particles in opaque, high solid content systems, it has not been widely used for characterising the liquid phase. This work presents a new, neutrally buoyant, alginate hydrogel tracer, designed to emulate the density of the liquid phase, which is suitable for high-speed tracking with PEPT.PEPT experiments were conducted in a bench-scale flotation cell, comparing the new tracer to ion-exchange resin tracers previously used in this system. Results showed statistically significant differences in pathlines, residence time and velocity distribution among the tracers. Moreover, the hydrodynamics of the new tracer agree with existing CFD predictions for the liquid phase. This methodology enables the comprehensive study of relative flow behaviour in complex multiphase systems.
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A database for the stocks and flows of sand and gravel, Resources, Vol: 11, Pages: 1-17, ISSN: 2079-9276
Increasing demand for sand and gravel globally is leading to social, environmental, and political issues that are becoming more widely recognised. Lack of data and poor accessibility of the few available data contribute to exacerbating these issues and impair evidence-based management efforts. This paper presents a database to store stocks and flows data for sand and gravel from different sources. The classification system underlying within it builds on the Universal Materials Information System (UMIS) nomenclature, which is used to construct hierarchical order in the data and in the same manner as the Yale Stocks and Flow Database (YSTAFDB), a common data format. To illustrate how the database is built and used, a case study using UK data is presented. The UK is chosen owing to relatively better access to data compared to other locations. Quantitative analyses of the data show the supply chain of these materials to be currently stable for the UK as indigenous extraction contributes 95.6% to UK sand and gravel production, with imports accounting for the rest of the inputs, of which 50% is reliant on only one nation.
Deveci M, Gokasar I, Brito-Parada PR, 2022, A comprehensive model for socially responsible rehabilitation of mining sites using Q-rung orthopair fuzzy sets and combinative distance-based assessment, Expert Systems with Applications, Vol: 200, Pages: 117155-117155, ISSN: 0957-4174
Mining companies play a critical role in developing mineral wealth across the globe. Interacting effectively with local communities is yet another potential source of long-term profitability, because of the opportunities that are not accessible if community engagement is not achieved. The financial advantages of a positive company image can be linked to attracting and retaining employees, as well as sustaining or even enhancing the capacity to do business with local suppliers. The socially responsible rehabilitation of a site after mine closure can facilitate access to new or former jobs for the mine workers. This study focuses on how to identify the best rehabilitation strategy after the closure of a mining site. In particular, a q-rung orthopair fuzzy sets (q-ROFSs) based CODAS (COmbinative Distance-based ASsessment) model is developed to support the evaluation of socially responsible rehabilitation activities in mining sites. To test and validate the model, the proposed methodology is compared to the ARAS (Additive Ratio Assessment) method. The results show that rehabilitation and social transition subsidy is the best alternative among those considered. Implementation of this alternative benefits the mining companies and also brings social benefits to the mine workers and the wider communities within the mining site.
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A Database for the Extraction, Trade, and Use of Sand and Gravel (Retraction of Vol 11, art no 38, 2022), RESOURCES-BASEL, Vol: 11
Singh DK, Brito-Parada PR, Bhutani G, 2022, An open-source computational framework for the solution of the bivariate population balance equation, Computers & Chemical Engineering, Vol: 161, Pages: 107780-107780, ISSN: 0098-1354
The bivariate population balance equation (PBE) is a mathematical framework to explain the evolution of polydisperse multiphase systems. In this work, the direct quadrature method of moments (DQMOM) is implemented in an open-source CFD code, Fluidity, for the numerical solution of bivariate PBE. This efficient numerical framework is a highly-parallelised finite element (FE) CFD code that allows for the use of mesh adaptivity on fully-unstructured meshes. Various test cases to solve spatially homogeneous bivariate PBEs with aggregation, breakage, growth and dispersion were simulated and verified against analytical solutions, resulting in excellent agreement. Benchmarking, by comparison with the Monte Carlo method solutions from the literature, with realistic kernels in a gas–liquid system for simultaneous bivariate aggregation and breakage was also performed to show the feasibility of this implementation for realistic applications. This open-source framework demonstrates its impressive potential in the case of bivariate PBE and can be exploited for the simulation of complex polydisperse multiphase systems.
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A Database for the Extraction, Trade, and Use of Sand and Gravel, RESOURCES-BASEL, Vol: 11
Cole K, Brito-Parada PR, Hadler K, et al., 2022, Characterisation of solid hydrodynamics in a three-phase stirred tank reactor with positron emission particle tracking (PEPT), Chemical Engineering Journal, Vol: 433, Pages: 1-13, ISSN: 1385-8947
It is challenging to measure the hydrodynamics of stirred tank reactors when they contain multiphase flows comprising liquid, gas bubbles and particles. Radioactive particle tracking techniques such as positron emission particle tracking (PEPT) are the only established techniques to determine internal flow behaviour due to the inherent opacity and density of fluid and the vessel walls. The profiles of solids flow are an important tool for robust reactor design and optimisation and offer insight into underlying transport processes and particle–fluid–bubble interactions for applications such as froth flotation. In this work, measurements with PEPT were performed with two tracer particles differing in surface hydrophobicity to characterise the solids hydrodynamics in a baffled vessel agitated with a Rushton turbine. The location data from PEPT were averaged with time to estimate the probability density function (PDF) of particle velocity in individual voxels. The peaks of these voxel distributions were used to produce profiles of solids flow in different azimuthal and horizontal slices. Bimodal vertical velocity distributions were observed in the impeller radial jet which suggest the particles experienced trajectory crossing effects due to inertia. Statistical tests were performed to compare the velocity distributions of the hydrophilic and hydrophobic tracer particles, which indicated similar average flow behaviour in the liquid or pulp phase of the vessel and differences near the air inlet, in the impeller discharge stream and pulp–froth interface. With tracers designed to represent gangue and valuable mineral species, the differences in velocity reveal interactions such as bubble–particle attachment and entrainment.
Cole K, Barker DJ, Brito-Parada PR, et al., 2022, Standard method for performing positron emission particle tracking (PEPT) measurements of froth flotation at PEPT Cape Town, MethodsX, Vol: 9, Pages: 101680-101680, ISSN: 2215-0161
Positron emission particle tracking (PEPT) is a technique for measuring the motion of tracer particles in systems of flow such as mineral froth flotation. An advantage of PEPT is that tracer particles with different physical properties can be tracked in the same experimental system, which allows detailed studies of the relative behaviour of different particle classes in flotation. This work describes the standard operating protocol developed for PEPT experiments in a flotation vessel at PEPT Cape Town in South Africa. A continuously overflowing vessel with constant air recovery enables several hours of data acquisition at steady state flow and consistent flotation conditions. Tracer particles are fabricated with different coatings to mimic mineral surface hydrophobicity and size, and a data treatment derived from a rotating disk study is utilized to produce high frequency (1 kHz) location data relative to the tracer activity. Time averaging methods are used to represent the Eulerian flow field and occupancy of the tracer behaviour based on voxel schemes in different co-ordinate systems. The average velocity of the flow in each voxel is calculated as the peak of the probability density function to represent the peak of asymmetrical or multimodal distributions.•A continuously overflowing flotation vessel was developed for extended data acquisition at steady state flow.•The data treatment enabled the direct comparison of different particle classes in the flotation vessel.•The solids flow fields was described by the probability density function of tracer particle velocity measured in different voxel schemes.
Wang P, Brito-Parada PR, 2022, Dynamics of a particle-laden bubble colliding with an air-liquid interface, Chemical Engineering Journal, Vol: 429, Pages: 1-10, ISSN: 1385-8947
The collision, bouncing and potential bursting of air bubbles with air-liquid interfaces are key processes involved in the initial stage of foam formation. While fundamental studies of these processes, especially for gas-liquid-solid froth systems, are very valuable for a better understanding of various chemical engineering separation systems, these are scarce. This paper investigates the dynamics of rising bubbles, without particles attached and with various particle coverages, as they collide with an air-liquid interface. For uncoated bubbles, an increase in distance from the bubble releasing point to the air-liquid interface resulted in higher bubble approach velocities, although with minor changes in the velocity fluctuation frequency. This increase in approach velocity was not observed for bubbles with relatively high particle coverage. For particle-laden bubbles, the collision with the interface is associated with movement of the particles over the surface of the decelerating bubble. This particle motion on the bubble surface, combined with bubble shape pulsation, contributes to the kinetic energy dissipation of the approaching bubble. A damped oscillation model was derived to represent the velocity of the bubble interacting with the interface, which shows that the amplitude of the velocity decreases gradually with the increase in particle coverage. The damping coefficient in the model, introduced to quantify the influence of attached particles, is shown to increase with particle coverage, confirming the key role that particles play in bubble collision dynamics at an air-liquid interface and allowing, for the first time, the prediction of their behavior.
Aksoy DO, Ozdemir S, Celik PA, et al., 2022, Fusion of the microbial world into the flotation process, Mineral Processing and Extractive Metallurgy Review, Vol: 43, Pages: 1068-1082, ISSN: 0273-3706
The depletion of high-grade ore deposits, as well as the generation of large quantities of tailings by mining and metallurgical activities, necessitates an urgent search for not only more cost-effective, but also more eco-friendly methods of recovering minerals from low-grade deposits and secondary resources. Research in the bioflotation process appears to be an answer to this search, thanks to the contribution of the microbial world. This study constitutes the first systematic and the most comprehensive review on bioflotation. The bioflotation studies in the literature were examined in a certain chronological order and by classifying the reagents in terms of both their origin and their use in flotation. Aside from the benefits of bioreagents to the mining industry, the review attempted to reveal the issues that prevent the transition to industrial application. This review aims to raise awareness of future research opportunities for mining and biology researchers while also presenting current bioflotation studies.
Zhang H, Brito-Parada P, Neethling S, et al., 2022, VISCOUS FROTH LENS: STEADY-STATE ANALYSIS, Pages: 2164-2168
We extend the quasi-static foam simulation method into the steady-state viscous foam modelling. The simulation of steady-state viscous foam flow is transferred into a surface energy minimization problem with varying equivalent “surface tension” along foam films. We simulate the motion of a viscous froth lens propagating in a straight channel. We find the 120° rule used in dynamic simulations stimulates the deformation of the lens structure if the same resolution of the film discretization is used. The proposed method cannot replace a dynamic simulation when the unsteady flow process is of interest. However, the results by the proposed method suggest that the 120° rule for the interior threefold point could be inefficient for high driven velocities. This is because films are highly curved near the interior-three fold point for high driven velocities, which results in dynamic contact angles deviating from the 120° rule. We suggest that a more advanced “vertex dynamics” rule should be implemented to incorporate the effect of the dynamic contact angles at the interior three-fold point.
Marmiroli B, Rigamonti L, Brito-Parada PR, 2021, Life Cycle Assessment in mineral processing – a review of the role of flotation, The International Journal of Life Cycle Assessment, Vol: 27, Pages: 62-81, ISSN: 0948-3349
PurposeThe aim of this literature review is to investigate the role of the beneficiation stage in the Life Cycle Assessment (LCA) of metals and minerals with a focus on the flotation process.MethodsThe systematic literature search included LCA studies comprising the beneficiation stage in their system boundaries and resulted in 29 studies that met the criteria requirements and were analysed. First, the system boundaries are investigated, along with the level of detail in the description of the sub-processes (e.g. flotation) and data granularity. Then, the life cycle inventories are scrutinised: data transparency and the relation between system granularity and data availability is commented. Of particular relevance, the way in which the functional unit is dealt with is examined. Finally, studies impact assessments are compared and discussed, and key parameters are highlighted.Results and discussionFor system boundaries, beneficiation is generally embedded into the mining stage. Even when described on its own, important sub-processes (e.g. flotation) are not considered, except for eight cases analysed. Functional unit definition is hindered by the output of the system being an intermediate product. Indeed, most studies use a declared functional unit but fail to provide its relevant characteristics, which is essential for a correct interpretation of results and for comparisons. Most studies rely on secondary data, not always presented transparently, to describe beneficiation. Results on the role of beneficiation in the metal value chain environmental impacts are conflicting, partly because of its site dependency. Site-dependent parameters found to be determining are ore grade, energy mix, mining technique, concentrate grade and ore mineralogy.ConclusionsThe flotation process, and more generally the beneficiation stage, is typically overlooked in LCA studies despite its growing relevance. Beneficiation not being assessed as a standalone stage, detailed in its subprocess
Mesa D, Cole K, van Heerden MR, et al., 2021, Hydrodynamic characterisation of flotation impeller designs using Positron Emission Particle Tracking (PEPT), Separation and Purification Technology, Vol: 276, Pages: 1-19, ISSN: 0950-4214
Impellers play a key role in flotation cells, as the turbulence generated through agitation aids particle suspension, air dispersion and particle–bubble collision. Therefore, it is important to understand the effect that different impeller designs have on flotation hydrodynamics, as small variations could enhance flotation performance. The study of flotation hydrodynamics is, however, a complex task due to the nature of flotation systems, which are opaque, multiphase, and polydisperse. In this paper, the impact of impeller design modifications on the hydrodynamics of a flotation cell was quantified for the first time in a three-phase system. Two different impeller designs, with and without a stator, were assessed using positron emission particle tracking (PEPT), a technique that allows the position and velocity of radioactive particle tracers within an opaque vessel to be determined. A novel PEPT data analysis strategy, as well as a statistical analysis on the basis of the Jensen–Shannon distance, were used. This statistical analysis, applied for the first time to PEPT data, facilitated the comparison of the different designs, by generating a robust quantification of their hydrodynamic differences. The experimental results showed that the stator significantly modified the hydrodynamics within the flotation cell, distorting the lower mixing loop that is characteristic of radial impellers. The use of a stator also resulted in the reduction of particle velocity and swirling outside of the impeller–stator region, both at the level of the impeller and, notably, at the pulp–froth interface. These findings have important implications for impeller–stator design, evidencing that the impeller has a direct effect on the hydrodynamics of the pulp and froth.
Promentilla MA, Beltran A, Orbecido A, et al., 2021, Systems approach toward a greener eco-efficient mineral extraction and sustainable land use management in the Philippines, Chemical Engineering Transactions, Vol: 88, Pages: 1171-1176, ISSN: 1974-9791
As the world transition towards a low-carbon future through renewable energy, mining of minerals and metals to attain this goal is substantial. The Philippines will play an important role in such global economy as it is the world’s fifth most mineral-rich country. However, their exploitation has not been maximized to benefit society. Benefits from the mineral resources sector remain less than 2 % of the country’s GDP since 2006, and the mining and mineral processing, including abandoned or legacy mines, are perceived negatively by the public. In low- and middle-income countries with weak implementation of mining and environmental legislation, the mining industry still operates in a linear system which is considered unsustainable. The mining, mineral extraction and processing, and metal extraction are designed to maximize profits with little plan on how to effectively manage mine wastes, protect the environment, transform post-mining land for beneficial use and empower impacted communities. This paper, thus, proposes a systems approach toward greener eco-efficient mineral extraction and sustainable land use management (SAGES). This approach will facilitate a paradigm shift, which is necessary to manage the country’s mineral endowments sustainably without compromising future land use of mining areas while at the same time supporting the needs and aspirations of the impacted host communities. It envisions extending the usability of mining areas beyond the life of the mine and integrating circular economy principles in addressing holistically mine waste management problems. The multi-R framework, originally developed in waste management (Reduce, Reuse, Recycle) and extended to circular economy strategies, has potential applications in mine waste management in the Philippines. An illustrative case study is then presented that employs a multi-R framework to address the mine waste in an operating Ni-laterite mining site.
Quintanilla P, Neethling SJ, Mesa D, et al., 2021, A dynamic flotation model for predictive control incorporating froth physics. Part II: Model calibration and validation, Minerals Engineering, Vol: 173, Pages: 1-15, ISSN: 0892-6875
Modelling for flotation control purposes is the key stage of the implementation of model-based predicted controllers. In Part I of this paper, we introduced a dynamic model of the flotation process, suitable for control purposes, along with sensitivity analysis of the fitting parameters and simulations of important control variables. Our proposed model is the first of its kind as it includes key froth physics aspects. The importance of including froth physics is that it improves the estimation of the amount of material (valuables and entrained gangue) in the concentrate, which can be used in control strategies as a proxy to estimate grade and recovery.In Part II of this series, experimental data were used to estimate the fitting parameters and validate the model. The model calibration was performed to estimate a set of model parameters that provide a good description of the process behaviour. The model calibration was conducted by comparing model predictions with actual measurements of variables of interest. Model validation was then performed to ensure that the calibrated model properly evaluates all the variables and conditions that can affect model results. The validation also allowed further assessing the model’s predictive capabilities.For model calibration and validation purposes, experiments were carried out in an 87-litre laboratory scale flotation tank. The experiments were designed as a randomised full factorial design, manipulating the superficial gas velocity and tailings valve position. All experiments were conducted in a 3-phase system (solid-liquid–gas) to ensure that the results obtained, as well as the behaviour of the flotation operation, are as similar as possible to those found in industrial flotation cells.In total, six fitting parameters from the model were calibrated: two terms from the equation for overflowing bubble size; three parameters from the bursting rate equation; and the number of pulp bubble size classes. After the mode
Quintanilla P, Neethling SJ, Navia D, et al., 2021, A dynamic flotation model for predictive control incorporating froth physics. Part I: Model development, Minerals Engineering, Vol: 173, Pages: 1-23, ISSN: 0892-6875
It is widely accepted that the implementation of model-based predictive controllers (MPC) ensures optimal operation if an accurate model of the process is available. In the case of froth flotation, modelling for control purposes is a challenging task due to inherent process instabilities. Most models for control have only focused on the pulp phase rather than the froth phase, which is usually oversimplified or even neglected. Despite the fact that froth stability can significantly affect the overall performance of flotation cells, there is still a gap in literature regarding flotation models for control purposes that properly include froth physics.In this paper we describe the development of a dynamic flotation model suitable for model predictive control, incorporating equations that describe the physics of flotation froths. Unlike other flotation models for control in the literature, the model proposed here includes important variables related to froth stability, such as bursting rate and air recovery, as well as simplified equations to calculate froth recovery and entrainment. These model equations allow estimating the amount of valuable material reporting to the concentrate, which can be used as a proxy to estimate grade and recovery. Additionally, pulp-froth interface physics was also included in our model, which enables a more accurate prediction of relevant flotation variables.A sensitivity analysis of the parameters showed that two out of seven parameters were highly sensitive. The highly sensitive parameters are the exponential factor n of the equation for the overflowing bubble size, and the constant value a of the equation for the bursting rate. Although the other parameters showed a reasonably lower sensitivity than n and a, the results also revealed that there is a significant difference in the prediction accuracy if the parameters are poorly estimated. Further simulations of important variables for control exhibited a good adaptability to changes in typ
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.