Curriculum Vitae

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Gilberto A. Pinto, Fernando O. Durão, António M. A. Fiúza, Margarida M. B. L. Guimarães and C. M. Novais Madureira, “Design Optimisation Study of Solvent Extraction: Chemical Reaction, Mass Transfer and Mixer–Settler Hydrodynamics”, Hydrometallurgy, Volume 74, Issues 1-2, pp. 131-147, August 2004, ISI Web of Knowledge: Times Cited: 3, References: 35

It is a well-known fact that a typical engineering design problem usually deals with more than one design criterion. If each design criterion is stated as an objective function to be optimised, then the engineering design problem becomes a multicriteria optimisation problem, requiring the simultaneous optimisation of more than one objective function.

In this paper, it is shown how the design of solvent extraction flow-sheets can be stated as a multicriterion optimisation problem, using the positive weighted sum approach. This is used not only to obtain parametric optimisation (i.e., the best operating conditions: agitation speed, residence time and phase flow ratio) but also to help in structural optimisation (i.e., to synthesise the best process flow-sheet: number of stages, flow structure and phase recycle ratio). We demonstrate this over a case study, namely, the selective separation of two chemically akin and hard to separate metals, zinc and cadmium, commonly found together in the leaching liquor of complex ores.

With this case study, it is shown that the design solutions are richer and more wide-ranging when put together from the vantage point of multicriterion optimization, whereas they become narrow-minded and/or biased if the starting point is a single criterion point of view. Three other conclusions of less general validity were also obtained: (i) the opposite effects of feed phase flow-rates on recovery and purity; (ii) the high sensitivity of short optimum residence times to variations in agitation speed; (iii) the ability of counter-flow associations of a variable number of mixer–settler units to accommodate changes in metal purity and overall recovery in response to drivers in market prices and environmental policies.

  1. M. L. Dinis* and A. Fiúza, “Simulation of Liberation and Dispersion of Radon from a Waste Disposal”, in “Environmental Contamination from Uranium Production Facilities and their Remediation”, Proceedings of an International Workshop, Lisbon, 11–13 February 2004, published by Internacional Atomic Energy Agency, Vienna, Pg. 63 a 70, ISBN 92-0-104305-8, STI/PUB/1228.

Radon emissions from a radioactive waste disposal may constitute a major source of environment contamination and subconsequently a potential health hazard to the nearby population. Radon-222 gas is generated from the radioactive decay of Radium-226 present in the particles. When it is formed, radon is free to diffuse along the pores of the residues to the surface and escape to the atmosphere.

Waste management and long term stabilisation has a major concern in reducing radon emissions to near-background levels. The common theoretical approach is done by calculating the cover thickness that allows a radon flux inferior to a stipulated and accepted value. The fundamentals of the conceptual model are based in the principles of diffusion across a porous medium, which allows the mathematical description of the radon transport through the waste and the cover.

The basic diffusion equations are used for estimating the theoretical values of the radon flux formed from the decay of the Radium-226 content in the waste material. The algorithm incorporates the radon attenuation originated by an arbitrary cover system placed over the radioactive waste disposal. As an alternative, it can be estimated the thickness of the cover that allows a radon flux inferior to the acceptable one.

Once the Radon is released into the atmosphere, it is available for atmospheric transport by the wind. Radon atmospheric dispersion is modelled by a modified Gaussian plume equation which estimates the average dispersion of radon released from a point source representative of one or several uniform area sources. The model considers the medium point release between all the areas contaminated. The concentration available for the dispersion is calculated from the total flux released. The dispersion can be simulated in different wind directions, with different wind velocities, as well as in the dominant wind direction.

  1. Padrão M.J., Fiúza A., “Remediation of a Sandy Soil Contaminated With Petroleum Products By Landfarming“, Paper B-02, in: M. Pellei and A. Porta (Eds.), Remediation of Contaminated Sediments—2003. Proceedings of the Second International Conference on Remediation of Contaminated Sediments (Venice, Italy; 30 Sep–3 Oct 2003). ISBN 1-57477-143-4, published by Battelle Press, Columbus, Ohio,

The knowledge of the biodegradation kinetics of petroleum products in a contaminated soil is very important for the comprehension of the mechanisms involved, as well as for an effective design of the selected technologic variant. Laboratory studies were conducted using bioreactors containing two types of contaminated sandy soil samples: one with diesel and another with crude oil. Both were collected in spillages locations. The microbial activity was stimulated through aeration and addition of a solution enriched in nutrients. The soils were sampled every week in order to determine the pH, the moisture content, the bacterial population, the nutrients and the contaminant concentration. The degradation rates were quantified based upon changes in the total petroleum hydrocarbons (TPH) concentrations. The experimental data provided the basis for the development of a comprehensive model describing simultaneously the time evolution of biomass and contaminant degradation. Several phenomena were globally taken into account in the kinetic models: the volatilisation, a fast kinetics component, a slow kinetic component and the refractory hydrocarbons for the time scale used in the experiments. This model is in turn linked to the kinetics of the biomass evolution. The proposed methodology is hereby exemplified by its application to the crude oil sample.

  1. Fiúza A., Vila Cristina,Respirometry Studies In An Hydrocarbon Contaminated Sandy Soil“, Paper C-01, in: M. Pellei and A. Porta (Eds.), Remediation of Contaminated Sediments—2003. Proceedings of the Second International Conference on Remediation of Contaminated Sediments (Venice, Italy; 30 Sep–3 Oct 2003). ISBN 1-57477-143-4, published by Battelle Press, Columbus, Ohio,

Since the last five years our research team has been studying several approaches to the bioremediation of soils contaminated with petroleum compounds. In a preliminary stage we studied the evidence of biodegradation of Total Petroleum Hydrocarbon (TPH) and its kinetics, as well as the kinetics of the abiotic degradable component of TPH. It was also possible to quantify a refractory component of the contaminant for the time scale of the experiments. A mathematical model describing the degradation of crude oil, both by abiotic and biologic processes, was developed. Searching the relationships between the crude consumption and the biologic activity a different approach was tried: the respirometry. Such respirometry studies were performed using a SableSystems TR8 respirometer, which is basically composed by an air dryer, a pump, a reactor (the soil container) and analysers for oxygen and carbon dioxide. The apparatus was connected to a computer that acquires and records the data. The results were statistically treated by different mathematical tools. The evolution of the oxygen concentration in time clearly shows a trend and a seasonality (daily cycles) that permits forecasting based on time series analysis. The mathematical and phenomenological linkage between the two approaches is currently under development.

  1. Padrão M.J., Fiúza A., “Respirometric Techniques in a Landfarming Study , Proceedings of the Second European Bioremediation Conference, organized by the Technical University of Crete, Pg 99 – 102, Supported by the High Level Scientific Conferences Programme and the Hellenic Ministry of Environment.

The technology known as landfarming has been widely and successfully used for removing petroleum hydrocarbons from contaminated soils.

Laboratory experiments were conducted to study the bioremediation potential of a sandy soil contaminated with crude. The sample was collected from the local of occurrence of existing spillage. The microbial activity was stimulated through aeration and the addition of a solution enriched in nutrients. The soil was sampled weekly in order to determine the pH, the moisture, the bacterial population, the nutrients content and the contaminant concentration.

One innovative step in our methodology was the performance of an uncommon respirometric test - the SOUR (Specific Oxygen Uptake Rate), as proposed by Lasaridi and Stentiford. The procedure makes use of a dissolved oxygen meter to measure the changes in the oxygen concentration of an aqueous soil suspension, at 30ºC. The alteration in the microbial respiration activity reflects the progress of the landfarming process. As the biodegradation occurs, less substrate is available to the microorganisms and this is reflected in their respiratory activity. The SOUR test revealed to be a simple, reliable and fast method to quantify indirectly the evolution of the biodegradation.

  1. Fiúza A., Vila Cristina,Bioremediation of a Sandy Soil Polluted by Petroleum Hydrocarbons – Respirometric Studies , Proceedings of the Second European Bioremediation Conference, organized by the Technical University of Crete, pg. 55-58, Supported by the High Level Scientific Conferences Programme and the Hellenic Ministry of Environment.

The soil contamination of a refinery area located in northern Portugal has been studied since last decade by our team, aiming a deeper understanding of the physical, chemical and biological characteristics of the involved phenomenology. Bioremediation, as a general family of processes, has been thoroughly studied in a laboratory scale, considering several distinctive approaches. The soil samples for these studies were collected in the proximity of some tanks for crude oil storage.

In a preliminary stage we studied the evidence of biodegradation of TPH (Total Petroleum Hydrocarbon) and its kinetics, as well as the kinetics of the abiotic degradable component of TPH. It was also possible to quantify a refractory component of the contaminant for the time scale of the experiments.

Searching the relationships between the crude consumption and the biologic activity, a second stage began using a different approach. The scale of the study was magnified, by submitting the contaminated soil to several respirometric experiments. Such respirometry studies were performed in a SableSystems TR8 respirometer, which is basically composed by an air dryer, a pump, a reactor (the soil container) and analysers for oxygen and carbon dioxide. The apparatus was connected to a computer that acquires and records the data.

The results were statistically treated by different approaches. The evolution of the oxygen concentration in time clearly shows a trend and a seasonality (daily cycles) that permits forecasting based on the system analysis theory. The mathematical and phenomenological linkage between the two approaches is currently under development.

  1. Fiúza A., Vila Cristina, “Application of Multivariate Statistics to Underground Water Samples Contaminated with Petroleum Products”, 8th International FZK / TNO Conference on Contaminated Soil CONSOIL, Gent, Pg. 746-753, 2003.

In order to perform a contamination survey in a complex location, where several types of petroleum products existed simultaneously, it was decided that it would be advantageous to establish a previous definition of contamination patterns. The data consisted in the results obtained by chemical analysis of different types of hydrocarbons existing in groundwater samples, collected from piezometers at the location.

The methodology here presented proceeds by steps, beginning from very simple multivariate statistics proceedings towards the most sophisticated. The first step was the construction of the correlation coefficients matrix between variables (concentrations). The single conclusion inferred was the high correlations between BTEX compounds, its individual components and the gasoline range hydrocarbon (GRO). A Principal Component Analysis that allowed us to detect three different patterns followed it.

The R-Mode Factor Analysis confirmed the previous statements and allowed to distinguish four composition patterns. The Q-Mode Factor Analysis allowed a net separation of the uncontaminated samples and all the others that were, at the same time, discriminated into three different patterns.

Finally, a Correspondence Analysis, were the objects (piezometers) and the variables (concentrations) were reduced to the same metric, clearly allowed the net definition of different contamination patterns and simultaneously evidenced the nature of transition (progressive or abrupt) between these patterns.

Finally, the data clustered by contamination pattern was treated by geostatistics, ascertaining the space distribution of the concentrations. This proved to be coherent with other physical information as, for instance, the relation between the location of the contaminations, its probable origin and the topography of the bedrock.

  1. Fiúza A., Futuro A., “Produtos Não Energéticos das Indústrias Extractivas - Minérios Metálicos e seus Concentrados (”Non-Energetic Products in Extractive Industries – Metallic Ores and its Concentrates”), National Inventory of Industrial Wastes, FEUP – INR, February 2003, 229 pages.

A exploração e tratamento de minérios metálicos em Portugal é hoje em dia extremamente reduzida. Apenas se encontram em actividade regular duas empresas: a Somincor que explora os jazigos da área de Neves-Corvo e a Beralt que explora o jazigo da Panasqueira. Existem ainda actividades minúsculas de recuperação de estéreis e escombreiras. Apesar deste facto, as produções de cobre, estanho, volfrâmio e prata são ainda significativas em termos de produção na comunidade europeia alargada. A Somincor utiliza a deposição dos resíduos sob via húmida, o que constitui a solução mais aceitável para os minérios sulfurados, enquanto que a Beralt tem milhões de toneladas de resíduos herdados das empresas que a antecederam na exploração da mina, que se encontra em actividade contínua há mais de um século.

Assim, o grande problema relativo ao armazenamento dos resíduos de minérios metálicos é o enorme passivo ambiental produzido em antigas explorações, cobrindo todos os distritos do País. Foi recentemente completado pelo Instituto Geológico Mineiro (Janeiro de 2003) uma inventariação, quase exaustiva, dos principais armazenamentos existentes no País que foram vistoriados e classificados preliminarmente de acordo com a sua potencial perigosidade aparente. Este estudo, de enorme valia, foi aqui parcialmente incorporado na forma de fichas individuais por cada local considerado, produzindo-se assim uma inventariação que contempla simultaneamente não só a listagem dos locais, mas que também qualifica individualmente cada local em termos de risco potencial.

Apresenta-se ainda neste estudo, com relativo detalhe, as relações entre a composição do minério e o processo de tratamento para produção de concentrados utilizado (em especial a intensidade da moagem) com os impactes potenciais adversos que podem vir a ser gerados, potencialidade essa que já se tornou efectiva em alguns casos mais graves. A situação mais grave, a chamada drenagem ácida, produzida pelos minérios piritosos, é aqui teoricamente analisada. Salienta-se que uma vez iniciadas as reacções envolvidas neste conjunto fenómeno é extremamente difícil controlar ou impedir a sua continuação.

Analisam-se ainda criticamente as soluções que foram utilizadas e sugerem-se as tecnologias mais convenientes para explorações ambientalmente sustentáveis.

  1. Fiúza A., Futuro A., “Minérios e Concentrados de Urânio e Tório (Uranium and Thorium Ores and Concentrates)”, National Inventory of Industrial Wastes, FEUP., INR, February 2003, 56 pages

Os minérios radioactivos foram explorados em Portugal praticamente durante todo o século XX (entre 1908 e 2000), predominantemente nos distritos de Viseu e da Guarda. Apesar de não existirem presentemente actividades de exploração e tratamento de minérios uraníferos o passivo ambiental acumulado, na forma de armazenamentos de resíduos de vários tipos, é enorme. Nos resíduos encontra-se acumulada grande parte da radioactividade original que se encontrava nos minérios (pelos menos 75%) e os seus efeitos potenciais no ambiente mantêm-se durante milhares de anos, atendendo aos longos períodos de semi-vida dos isótopos radioactivos. As condições em que os armazenamentos de resíduos foram efectuados não foram as mais convenientes e eram, desde o fim do decénio de 70, desajustadas relativamente às práticas europeia e americanas existentes então no sector. Alguns dos estudos efectuados sobre os potenciais efeitos ambientais desses armazenamentos, apesar do seu carácter pontual e não sistemático, sugerem a existência de efeitos nocivos adversos cuja real amplitude deve ser quantificada.

  1. Meira A.C., Fiúza A., “Experimental Assessment of Pressure Drop in Air Stripping Columns”, Proceedings of the 4th International Conference on Calibration and Reliability in Groundwater Modelling (ModelCARE 2002), Published by Univerzita Karlova v Praze, Pg. 451-454.

Abstract: One important step in the design of air stripping operations for the removal of VOC is the choice of operating conditions, which are based in the phase ratio. This parameter sets on directly the stripping factor and the efficiency of the operation. Its value has an upper limit determined by the flooding regime, which is previewed using empirical correlations, namely the one developed by Eckert. This type of approach is not suitable for the development of algorithms. Using a pilot scale column and a convenient solution, the pressure drop was determined in different operating conditions and the experimental values were compared with the estimations. This particular research will be incorporated in a global model for simulating the dynamics of air stripping using a multi variable distributed parameter system.

  1. António Fiúza, “An introduction to partial differential equations – Introduction, Modelling and Resolution using the Matlab, integral transforms and Numeric solutions by discretization”. Pedagogic text for the students of the Master in Environmental Engineering. 65 pages.

  1. António Fiúza, “Modelos de Dispersão Ambiental (Models for Environmental Dispersion)”, Didactic Text for the students of the Licentiateship in Environmental Engineering, 65 pages

  1. António Fiúza, “Instrumentação (Instrumentation)”, Didactic Text for the students of the subject Instrumentation and Control (Licentiateship in Mining and Geo-Environment T 65 pages.

  1. Reabilitação de Solos - Relatório de Investigação Preliminar sobre o Subsolo no Interior da Refinaria da Petrogal em Leça da Palmeira. (Soil Remediation – Repport on the Preliminary Evalution of the subsoil contamination at the Petrogal Refinery)

Estudo genérico sobre a dispersão e intensidade da contaminação dos solos em produtos petrolíferos abrangendo os seguintes temas: Caracterização preliminar do subsolo e suas propriedades, propriedades dos produtos petrolíferos condicionantes do destino ambiental e concentrações de risco, Interpretação e tratamento exaustivo dos dados obtidos em campanhas anteriores, Amostras recolhidas em Dezembro de 2000 – Análise e Interpretação, Medidas de Mitigação, Passos Futuros de Investigação. 137 pages.

  1. G.A. Pinto, M. Baptista, A. Guedes, M.Guimarães, C. Madureira, A.M. Fiúza, J. Cruz Pinto, “Model Validation for Mixer-Settler Units”, Comunication to the “Chemical Engineering 6th World Congress”, Melbourne, Australia.

Mass transfer processes between immiscible liquid phases play an important technical and economical role in the chemical, mining and environmental industries, because of their large throughput capacity and reduced energy and environmental costs, small energy and environmental costs. The simplicity, flexibility and ease of construction and of operation of their mixer-settler implementation explain its worldwide popularity. Up to now, the complexity of the hydrodynamic sedimentation phenomena, however, have prevented the proper, first principles based, modelling approach to the design of their industrial set-ups and forced the use of the less flexible, empirical correlation based, scale-up approach, thus resulting in frequent oversizing of the industrial units. Associating two well-known, available, sophisticated but fast, continuous flow, steady-state models, the Guimarães (i) thoroughly agitated mixer model based on moment generating functions and the Ruiz (ii) finite-differences shallow-depth settler model, we have developed a simple and effective combined model and algorithm (for the combination). The input parameters for the combination model are volumetric flowrates, initial solute concentrations and relevant physical properties of the phases, and the agitation power density in the mixer. In order to validate the combined model, we have built and used pilot-scale experimental set-ups in which mixer inner drop-size distributions and settler length and depth of the dispersion wedge may be optically measured. Results of the parameter optimisation are encouraging and further measurement of the dropsize distributions is considered. Preliminary test results indicate the potentiality of the algorithm for the efficient sizing of the units and the prediction of their combined performances in complex networks involving roughing, cleaning and reclaiming stages.

  1. C. Vila, O.C. Nunes, A. Fiúza, A Model of biodegradation of Crude Oil in Soils, Proceedings of the First European Bioremediation Conference, organized by the Technical University of Crete, Supported by the High Level Scientific Conferences Programme and the Hellenic Ministry of Environment, Pag 1- 5.

A new model of biodegradation of crude oil is currently under development. Based on experimental data it was possible to develop a component of this mathematical model to describe the behaviour of biomass growth and substrate consumption.

Microorganisms were selected from a soil sample, collected nearby a crude oil tank located in an oil refinery situated in the northern part of Portugal. Several enrichments were made in two different growth media. The first one was composed by inoculum, crude oil, and mineral medium and, the second one was composed by inoculum, crude oil, mineral medium and yeast extract. Two different types of population were obtained. In order to obtain data for kinetic parameters, five separate cultures were grown in 10 ml flasks, for each type of consortium. The cultures were incubated at 30º C with 150 rpm. In a predefined schedule one flask of each type of consortium was picked up and all the content was extracted and analysed by gas chromatography (GC) with a flame ionisation detector (FID). In order to validate and generalise the model, it will be necessary to repeat the experiment, changing some parameters, namely the period of incubation and the composition of the media. As a research window for the future we have all the work involving the characterisation of the three consortia obtained.

  1. António Fiúza, “Limpeza e Reabilitação de Solos Contaminados (Mitigation and Remediation of Contaminated Soils)”, Pedagigic text for the students in Mining and Geo-Environmental Engineering and for the students of the Environmental Engneering Master. 298 pages.

  1. António Fiúza, “Relatório de Investigacão Preliminar sobre o Subsolo no Interior da Refinaria de Leça da Palmeira (Preliminary Repport – The contamination of the subsoil at the Petrogal Refinery”, Research conducted through a protocol with Petrogal, FEUP, Dez 2000, 150 pages

  1. Nunes A.L., Fiúza A., A Mathematical Model for Soil Vapour Extraction, em “Implementation of in Situ Remediation Techniques - Chlorinated Solvents and Heavy Metals", Pag. 177-180, Editors: D.A.Buck, M.J. Lexmond and P.W.M. Mullekom, Proceedings of the International Congress, Utrecht, Netherlands.

Soil vapour extraction is one of the most successful technologies in reducing the concentration of volatile organic compounds in the vadose zone of the soil. The main principle is the application of a vacuum source to the soil, using extraction wells. The pressure gradient initiates air flow through the contaminated soil, volatilizing the organic compounds which are dragged along with it to the vacuum source.

The work presented is a two-dimensional model for a single well which accounts for the peculiarities of simulating the cleaning of an area whose spatial distribution of contamination is already known.

The global model is divided into 3 main sub-models each accounting for some particular phenomena: convective transport, dispersive-advective flux, and volatilisation and contaminant removal. There is also a ‘main body’ which makes the connections between them. It produces the final outputs concerning the time evolution of contamination levels for solid, liquid and gaseous phases. All models involved are essentially dynamic systems with distributed parameters described by systems of partial differential equations, of given boundary and initial conditions, on a two dimensional discrete spatial domain. In the single case of the sub-model concerning the mass transfer between phases, a system of ordinary differential equations is used. The partial differential equations are solved numerically, by means of transformation to finite difference equations. These are then solved in an iterative manner for each cell, accounting for the discrete nature of the spatial domain.

  1. Fiúza A., Estratégia de Elaboração de um Plano de Reabilitação (Strategy for Elaborating a Corrective Action Plan), Comunication presented to the Conference “Strategies for Remediation of Soils and Waters in Urban and Industrial Environment”, Fundation of Science and Technology Faculties, Taguspark, Oeiras.

Propõe-se uma metodologia de elaboração de um Plano de Acção Correctiva encarado como toda a investigação conduzida desde a descoberta de um local contaminado e posteriormente confirmado como tal, até à elaboração de um projecto de reabilitação que inclui o seu próprio controlo e monitorização ambiental. Distinguem-se quatro fases distintas: 1 – Caracterização do Local e Análise de risco; 2 – Selecção preliminar das alternativas de reabilitação; 3 – Estimativa de todos os parâmetros relevantes para a elaboração de um projecto de engenharia do sistema de reabilitação seleccionado e 4 – Procedimentos de controlo e monitorização da tecnologia seleccionada.

    1. Fiúza A., Metodologia de Elaboração de um Plano de Acção Correctiva (Methodology for Elaborating a Correctiva Action Plan), Component of the High Doctorate Public Examination. Last class on teh subject Mittigation and Remediation of Contaminated Soils.

    1. Fiúza A., Programa, Metodologia e Didáctica da Disciplina Limpeza e Regeneração de Solos do Mestrado em Engenharia do Ambiente (Program, Methodology and Didatics of the Subject Mittigation and Remediation of Contaminated Soils), Component of the High Doctorate Public Examination.

    1. Fiúza A., Limpeza e Regeneração de Solos, Anex to the report concerning the program, the methodology and the didatics of the Subject Mittigation and Remediation of Contaminated Soils. Component of the High Doctorate Public Examination.

  1. Fiúza A., Minas e Geo-Ambiente: Uma Simbiose Contextual Necessária (Mining and Geo-Environment: A Necessary Contextual Symbiosis), VI Meeting of the Associacion Iberoamericana de Enseñanza Superior de la Mineria (AIESMIN), 8 pags., Oviedo, Spain.

O encerramento progressivo, irreversível no curto e médio prazo, as actividades mineiras, em Portugal e na Europa, criou uma provisória ausência de correspondência entre a organização curricular clássica da Engenharia de Minas e as suas necessidades sociais, as moribundas e as emergentes. A estrutura clássica assentava os seus objectivos fundamentais na satisfação das necessidades da actividade industrial mineira, com um espaço de actuação extremamente bem definido e com fronteiras relativamente rígidas. Contrariamente a outros campos de actividade, a Engenharia de Minas permaneceu concentrada em campos de actuação e de investigação demasiado restritivos por tempo excessivo. No entanto, as necessidades sociais presentes e as novas actividades emergentes, nomeadamente no diagnóstico e na reabilitação ambientais criaram novos espaços de actuação para os engenheiros de minas. A estrutura científica básica que lhes é exigida pelos novos domínios de actuação é praticamente a mesma que existia nos currículos clássicos e as novas tecnologias geo-ambientais têm íntima relação de parentesco com tecnologias mineiras. Com este objectivo a Faculdade de Engenharia da Universidade do Porto reformulou totalmente o seu plano de estudos nesta área da engenharia. Uma simbiose entre a engenharia de minas e o geo-ambiente foi a solução encontrada e é um objectivo para o futuro.

  1. Fiúza A.M.A., Sparse Matrices as a Practical Way to Solve Systems of Partial Differential Equations when the Boundary Conditions are in Opposite Locations, 2nd Meeting on Numerical Methods for Differential Equations, Pag. 490-500. Edited by P. Oliveira, F. Oliveira, F. Patrício, J. Ferreira, A. Araújo, Department of Mathematics, Coimbra, 1998.

A high number of technological operations involve mass transfer phenomena between two phases that flow counter-currently. These systems can be described by a system of partial differential equations where the response variables, or output variables, generally the concentrations in each different phase, are variable in space (ordinarily uni or bidimensional) and time.

The methodology used in studying the dynamics of these systems has two main steps:

(a) Calculation of the spatial variation of the output variables in steady-state conditions. In this particular situation the output variables are time independent; if there only one spatial coordinate the system of PDE becomes a system of ODE;

(b) Study of the evolution of the system in time and space when time dependent perturbations are introduced in input variables. In this second step the initial variables are replaced by deviation variables in relation to nominal conditions.

Very seldom the resulting system of PDE has previously known solutions, and it is not an easy task to find the analytical functions describing the response by the most common methods, for instance using integral transformations. For this reason it is a usual procedure to use numerical methods and among these the finite differences are a common and generalized alternative of easy implementation. But as we are dealing with a counter-current operation the boundary conditions are defined in the extreme opposite sides of the spatial coordinates. This situation requires the simultaneous usage of descending differences for one of the response variables (generally the concentration in one the phases) and ascending differences for the other. This particular set of boundary conditions usually denies the possibility of finding a recursive numerical strategy where solutions irradiate from the solving of the discretized system in each space-time cell, to the neighbouring cells. Under these conditions the numerical solution requires to solve a double system of algebraic equations for each space-time cell, which implies to solve a simultaneous system of thousands of algebraic equations to thousand of unknown variables. Even with large increments in space and time discretizations, the resulting systems are enormous and can not be solved due to restrictions in memory in ordinary personal computers.

Another peculiarity of the resulting system is the high number of zero elements in the system matrix. Under these circumstances the usage of sparse matrices allows the analytical resolution of the discretized system due to the high economy in memory generated. Simultaneously the time required for the calculations, which could be of several hours, suffers a shortage to the order of seconds, once the required amount of time is proportional to the number of arithmetic operations on nonzero quantities.

This methodology is applied to a paradigmatic distribute parameter model of a technological operation - dynamics of air stripping used for elimination of volatile organic compounds in underground water. The software used is MATLAB.

  1. Fiúza A.M.A., Vila C., A Distributed Parameter Model for Downward Percolation Leaching, 2nd Meeting on Numerical Methods for Differential Equations, Pag. 501-509, Edited by P. Oliveira, F. Oliveira, F. Patrício, J. Ferreira, A. Araújo, Department of Mathematics, Coimbra, 1998.

The first mathematical models of dissolution were developed as early as 1846 for very simple and idealised situations. Since then, many other models have been developed, generally using semi-empirical relationships. A new mathematical model totally based on the phenomenology of heap leaching is proposed. Formally, the model is a distributed parameter system where all the parameters have a precise physical sense which allows measuring them in a laboratory.

The model consists of a three first order partial differential equations system, the first describing the space-time evolution of the concentration of the leaching agent. The second one outlines the behaviour of the metal in the solid phase in the same domain, and the last one describes the variation of the concentration in metal transferred from solid phase to liquid as a consequence of the depletion in the leaching agent.

The physical reality undoubtedly defines both the initial and the boundary conditions. It also suggests a chained integration sequence and the applicability of numerical methods. Because there is not a known analytical solution for the system of PDE, numerical methods – finite differences – were used. The stability of the solution was studied in detail as a function of discretization of the domain.

The simulations performed using the model showed a high agreement when compared to experimental data, proving its robustness.

  1. Fiúza A.M.A., Meira A.C., A New Approach in the Design of Air Stripping Columns for the Treatment of Groundwater Contaminated with Volatile Organic Compounds, 2nd Meeting on Numerical Methods for Differential Equations, Pag. 480-489, 10 pages, Edited by P. Oliveira, F. Oliveira, F. Patrício, J. Ferreira, A. Araújo, Department of Mathematics, Coimbra, 1998.

Volatile organic compounds are a common source of groundwater contamination that can be easily removed by air stripping in columns with random packing and using a counter-current flow between the phases. This work proposes a new methodology for the column design for any particular type of packing and contaminant avoiding the necessity of a pre-defined diameter used in the classical approach. It also renders unnecessary the employment of the graphical Eckert generalized correlation for pressure drop estimates. The hydraulic features are previously chosen as a project criterion and only afterwards the mass transfer phenomena are incorporated, in opposition to conventional approach. The design procedure was translated into a conventional algorithm using C++ as programming language.
1997 António Fiúza, Ana Cristina Castro, Tratamento de Água Subterrânea Contaminada por Compostos Orgânicos Voláteis. Considerações sobre o Dimensionamento e Simulação de Colunas de Arrastamento por Ar (Treatment of groundwater Contaminated with Volatile Organic Compounds. Considerations about Design and Simulation of Air Stripping Columns), Seminar on Groundwater, Portuguese Association of Hydrologic Resources (Associação Portuguesa dos Recursos Hídricos), Lisbon.
Volatile organic compounds are a common source of groundwater contamination that can be easily removed by air stripping in columns with random packing and using a counter-current flow between phases. We propose a new methodology for column design for any type of packing and contaminant: the hydraulic features are previously chosen as a project criterion and only afterwards the mass transfer phenomena are incorporated, in opposition to classical methods. A distributed parameter model for the dynamic simulation of the process is also proposed using a system of two non-linear partial differential equations.
1997 Fiúza A., Metodologia, Didáctica e Inovação Pedagógica de uma Disciplina de Aquisição e Análise de Dados (Methodology, Didatics and Pedagogic Innovation in Data Acquisition and Analysis), 2º Workshop on Application of Statistics to Engineering, Porto..
A disciplina “Aquisição e Análise de Dados” faz parte do currículo obrigatório dos alunos da Licenciatura em Eng. de Minas e da recém licenciada Licenciatura em Eng. de Minas e Geo-Ambiente, no seu terceiro ano de escolaridade universitária. Constitui um curso de formação de nível intermédio, sendo precedida por uma disciplina semestral de nível introdutório e carácter genérico (Métodos Estatísticos), no 2º ano, onde se abordam as noções básicas introdutórias à Teoria das Probabilidades e à Estatística Monovariável, e sendo seguida por outra especializada, Geo-estatística, leccionada no 5º ano da Licenciatura, e incidindo sobre a teoria das variáveis regionalizadas. A sua introdução curricular tem apenas quatro anos de existência.

A especificidade dos fenómenos abordados nesta Licenciatura implica a necessidade de uma formação matemática básica mais elevada que nos restantes cursos de Engenharia, exceptuando a Electrotécnica, e por razões distintas. Entre essas razões pode citar-se a extrema complexidade da realidade analisada nas ciências da Terra, que reside no facto de incidir sobre fenómenos naturais, em oposição à realidade construída dominante nas restantes engenharias, aos críticos problemas de amostragem, à complexidade dos processos industriais de tratamento e recuperação de recursos minerais, em que as características dos fluxos não podem ser apenas caracterizadas por uma simples concentração, tal como acontece nos processos químicos, mas porque trata de sistemas particulados se necessita, no mínimo, de distribuição bivariáveis, em calibre e em concentração. Analisam-se os obkectivos e conteúdo bem como a metodologia inovadora e interactiva de aprendizagem
1997 Fiúza A., Estudo Ecotoxicológico e de Impacte Ambiental da Oficina de Tratamento Hidrometalúrgico de Castromil (Ecotoxicological and Environmental Impact Study of the Castromil Hydrometallurgical processing Plant), in Estudo do Impacte Ambiental da Mina de Castromil.
1997 António Fiúza, Cristina Vila, Appraisal of Environmental Impact from Old Mining Tailings, in Environmental Biotechnology, Antwerp, Belgium.
Tailing disposals from ancient mining exploitations are a major source of soil contamination by heavy metal sin certain restricted and located areas. Dispersion in the environment by natural agents can affect large areas. We propose a methodology for evaluating the risk assessment resulting from such dispersion which includes, besides a global transfer model, some particular and restricted sub-models of transfer and fate.

1996 Programa, Métodos e Conteúdo da Disciplina Sistemas e Controlo do Mestrado em Tecnologia e Gestão de Recursos Minerais (Program, Methods and Contents of the subject Systems and Control, Master in Management of Mineral Resources), Written assessment for an open conquest for fulfilling a vacancy as Associate Professor at the Engineering Faculty, University of Porto.
1995 M. Cristina Vila, António Fiúza, Lixiviação por Percolação – Um Modelo de Parâmetros Distribuídos (Percolation Leaching – A Distributed Parameter Model), Estudos Notas e Trabalhos, I.G.M., 1995, Volume 37, pages 11 to 14.
Apresenta-se um modelo fenomenológico de parâmetros distribuídos para a lixiviação por percolação. O modelo foi testado e validado através dos resultados de ensaios de lixiviação para dois tipos de minério (um de urânio que se dissolve sob a forma de complexo aniónico e o outro de cobre que se dissolve na forma catiónica).

O modelo provou ajustar-se bem às realidades estudadas, revelando maior flexibilidade e aplicabilidade do que os modelos existentes neste domínio.
1995 Fiúza A., Models for Transport of Contaminants through Bottom Liners in Sanitary Landfillings, Aplicacion de los Metodos Geofisicos en el Estudio y Control de la Contaminacion de Suelos y Aguas, Oviedo, Spain, 1995.
Convection and diffusion are the transport mechanisms for dissolved contaminants in a liquid phase moving through solids. Diffusion is approximately represented by the ideal Fick Laws, while convection can be considered as a percolation process described by the Darcy Law. The unsteady transport of active sanitary landfilling leachates through impermeable bottom liners can be described by a distributed parameter model using simultaneously both mechanisms, while only diffusion is used for a post-closure situation. Both models, using typical values for the relevant parameters, are applied to clay liners, to synthetic geomembranes and to double liners. Space and time evolution of the contaminant concentration is obtained and breakthrough times are estimated. Model allows for design of liners and simulates space-time evolution either in operating circumstances, either after sealing.
1995 Fiúza A., An overview on Soil Remediation, Course and Workshop on “Soil and Groundwater Cleaning”, Comenius University, 6 pags, Bratislava, Slovakia.
The soil remediation technology is very recent and in certain cases the available techniques are younger than the kinetics of the process itself. On the other hand soil cleaning is performed with several different objectives, which restraints the possible applicable methods. The paper analyses the available confinement techniques (interceptor systems, lining, barriers and slurry wall), as well as post extraction techniques (Excavation, Enhanced volatilisation, Extraction, Biodegradation, Wet Oxidation and Stripping) and in-situ techniques (physical, chemical and biological). For each of them it is referred the class of contaminants that can be removed and the respective field of application – soil type and characteristics.
1995 Fiúza A., Design and Liner Materials for Sanitary Landfillings, Course and Workshop on “Soil and Groundwater Cleaning”, 10 pags, Comenius University, Bratislava, Slovakia.
Convection and diffusion are the transport mechanisms for dissolved contaminants in a liquid phase moving through solids. Diffusion is approximately represented by the ideal Fick Laws, while convection can be considered as a percolation process described by the Darcy Law. The unsteady transport of active sanitary landfilling leachates through impermeable bottom liners can be described by a distributed parameter model using simultaneously both mechanisms, while only diffusion is used for a post-closure situation. Both models, using typical values for the relevant parameters, are applied to clay liners, to synthetic geomembranes and to double liners. Space and time evolution of contaminant concentration is obtained and breakthrough times are estimated. Model allows for design of liners and simulates space-time evolution either in operating circumstances, either after final sealing.
1995 Fiúza A., Leachate Apportionment and Leachate Treatment in Sanitary Landfillings, Course and Workshop on “Soil and Groundwater Cleaning”, Comenius University, 9 pag., Bratislava, Slovakia.
Leachates are the main environmental problem originated by landfillings and the estimate of the expected production flowrates is an important factor in the design and project, both during operational period and after closure. A conceptual tool for such estimation is transient or unsteady water mass balances. The several inputs and outputs to and from the system are described and methods for accounting each of them are indicated. However, it is not only necessary to preview the quantity bur also the quality. Thus, the biological and chemical mechanisms of leachates production are analysed. Their understanding entitles possible strategies for process control. Finally, leachates can not anymore be discarded on the environment, percolating through the soil, for natural attenuation. For this reason, the principal methods of treatment by piping the leachates, by biological, physical or chemical methods are shortly described and analysed.
1994 Radiações e Impacte Radiológico (Radiations and Radiological Impact), Scholar Publication for the students attending this subject in the Master in Environmental Engineering, FEUP, 100 pages.
1994 Fiúza A., Teoria da Projecto e da Decisão Económica (Project and Economic Decision Theory), ), Scholar Publication for the students atennding the subject “Cost Engineering and Project Evaluation”, Graduation in Mining Engineering, F.E.U.P., Porto, 250 pages.
1994 Madureira C., Cavalheiro A., Fiúza A., Geostatistics as the art of inference from a single sample, Journal Geo-sistemas, nº3, 19 pages, 49—65.
The new distinctive problems of geostatistics, as an art of making statistical inference upon a single sample is, the need for sound, effective and theoretically supported

i) homogeneity tests, a problem into which we feel and have already made promising advances, although further research is needed into the probability function of the tests variants;

ii) multivariate statistical distribution laws applicable to processes in the real world, mainly in the field of generalization of the limit theorems;

iii) heteroscedasticity reducing techniques, a field where statistical research has been scarce, where results are generally empirical and where strenuous labour is anticipated.

1993 Fiúza A., Aquisição e Análise de Dados (Data Acquisition and Analysis), Scholar Publication for the students in Mining Engineering, F.E.U.P., Porto, 250 pages.
1993 Um Modelo Cinético da Lixiviação por Percolação (A Kinetic Model for Percolation Leaching), Congresso of the Portuguese Society of Materials (Sociedade Portuguesa de Materiais), Porto, pg. 407 a 420, 12 pag.
A fenomenologia envolvida na lixiviação por percolação é extremamente complexa encontrando-se numa fase muito preliminar de conhecimento. Apesar de existirem muitos modelos conceptuais, este baseiam-se em hipótese extremamente restritivas e não incorporam os parâmetros fundamentais para simulação, projecto e controlo: o débito específico de aplicação e a altura do material. Não permitem também descrever simultaneamente, de um modo coerente, a evolução temporal das concentrações e do seu integral, o rendimento da extracção. Alguns destes factos são explicitamente reconhecidos nas conclusões do relatório elaborado pelos laboratórios da Warren Spring para a C.E.E. As necessidades de interpretação experimental e de projectação conduziram a que tenhamos proposto e utilizado um modelo não fenomenológico que permite incorporar os parâmetros mais relevantes atrás mencionados.
1993 Simulation of the Unsteady-State Hydrodynamics of Interacting Liquid-Liquid Dispersions, International Solvent Extraction Conference, em colaboração com Ribeiro L.M., Guimarães L. M., Cruz-Pinto J.J.C, in Solvent Extraction in the Process Industries, Proceedings of the ISEC 93, in D. H. Logsdail and M.J. Slater (editors), Elsevier, 2, 1167.
In this work, the population balance model of Guimarães and Cruz-Pinto (1988) and Guimarães (1989) is extended to analyse the dynamic behaviour of turbulent agitated liquid-liquid dispersion, in a continuous flow stirred-tank collector. We attempt the direct numerical solution of the unsteady-state drop population balance equations, by adequate and precise time and drop volume discretization, and show that fast simulations of such complex behaviour are indeed possible and practical, such as to predict and portray the dispersed phase holdup and drop size distribution changes in the system. Perfect agreement has been obtained between the limiting, steady-state, dispersion properties predicted in this work and those previously obtained for identical cases by both the moment-generating function and Monte-Carlo simulation methods. The dynamics of the system was also studied after sudden changes in the phase flow rates, agitation intensity, etc., which are of significant practical relevance. The system’s transition to a new steady-state has been studied by following the evolution of the dispersed phase drop size distribution with time. From the dynamics of this transition, information can be derived on the system’s nature and its characteristic response times. The algorithm developed is also adequate to describe the transient and the steady-state of a batch vessel, as well as the mass transfer performance of agitated liquid-liquid contactors.
1992 Fiúza A., Dinâmica de Sistemas (System Dynamics), Scholar Publication for the students in Mining Engineering, F.E.U.P., Porto, 250 pages.
1992 Carlos Madureira, António Fiúza and Cardia Lopes, Estratégia de Projecto (Project Strategy), Scholar publication written for an intensive couse for the extractive industry, 600 pages, Porto,
1991 Plano Factorial de Experimentação e o Método de Crivagem das Variáveis de Plackett e Burman (Factorial Plan of Experiments and the Placket Burman Method for Screening Variables), Notes about a Conference made at I.S.E.P., April de 1991, 18 pages.
1991 Fiúza A., Hidromineralurgia (Hydrometallurgy), Scholar Publication for the students in Mining Engineering, Porto, 400 pages.
1991 Fiúza A. Carlos Madureira and Abílio Cavalheiro, Controlo e Automação (Automation and Control), Scholar publication written for an intensive couse for Mineral industry. 400 pages, Porto.
1990 Fiúza A., Introdução à Teoria do Controlo (Introduction to Control Theory), Scholar Publication for the students in Mining Engineering, Porto. 250 pages.
1989 Fiúza A., Fundamentação das Variáveis Essenciais do Projecto Mineiro - Aplicação a um Caso Exemplo (Foundation of Essential Variables in a Mining Project – Application to a Case Study), Ph. D. Thesis in Mining Engineering, Enmgineering Faculty, University of Porto. Around 600 pages.
A estrutura da informação necessária ao projecto mineiro não permite fundamentar nenhuma variável à priori. A sua conceptualização conduz a um sistema fechado onde cada relação é estabelecida uns pelos outros, num típico círculo vicioso ou dialelo. Normalmente é possível actuar sobre um vector de comando que, no nosso caso exemplo, comporta três ou quatro variáveis: o teor de corte, a cadência de exploração, o processo de tratamento e o teor de separação (se coexistir mais do que um processo simultaneamente). São estas as variáveis que denominamos essenciais e que são normalmente arbitradas com base na sensibilidade do projectista. Propõe-se uma metodologia de optimização global, mono ou multicritério. No capítulo 2 apresenta-se uma estrutura lógica dos componentes (sub-modelos) intervenientes que permitem romper o dialelo e que constituem o modelo conceptual. No capítulo 3 estudam-se relações quantitativas quantidade-qualidade e aplicam-se ao caso paradigmático seleccionado. No capítulo 4 apresenta-se uma modelagem quantitativa parametrizada da lavra. No capítulo 5 desenvolve-se uma metodologia para a determinação da recuperação média, alicerçando-se numa simbiose entre a hidrometalurgia, a avaliação de recursos e a mineralogia do jazigo. No capítulo 6 faz-se uma abordagem da alternativa relativa à lixiviação por percolação. No capítulo 7 modelam-se três processos hidrometalúrgicos alternativos. No capítulo oitavo estabelecem-se modelos simples de estimativa do investimento e de determinação do impacte ambiental. Finalmente, no último capítulo, constrói-se um modelo coerente e articulado de interacção entre todos os sub-modelos desenvolvidos.
1988 Alto Alentejo Mining Complex; Preliminary Feasibility Study, Reformulation of the Nisa project in a new Technological base. Document specially prepared for an international technical audit. 200 pages, Empresa Nacional de Urânio, E.P.
The Nisa Project is reformulated in a new technological basis considering heap leaching as the main processing operation. This document was specially prepared for an international technical audit which was later performed by Kilborn Engineering, Canada. All the aspects of the project were reviewed ant changed in accordance with the main processing option. This includes: Geology, Mining, Metallurgy, Plant Design, Plant Services and Infrastructures, Supply of Utilities, Capital Costs, Project Schedule, Operating Costs and Financing Evaluation.

  1. Fiúza A., Análise de Sensibilidade em Projectos Mineiros; Algumas Reflexões e Propostas Metodológicas (Sensibility Analysis in Mining Projects – Some Thoughts and Methodological Proposals); Mining Buletin, 23, 3º trimestre, Jul-Set 1986, pg. 167-175.

Às incertezas habituais de um empreendimento, o projecto mineiro acrescenta factores específicos de indeterminação derivados da sua própria natureza: o seu objectivo e âmago – o jazigo – é, ele próprio, inicialmente “desconhecido”. A sua dimensão qualitativa e quantitativa, estimada por interpretação e amostragem, não é fixa mas flutuante num espaço de coordenadas tecnológicas e económicas evolutivas.

Por outro lado, o seu domínio de existência raramente é o mercado interno e o preço da produção quase nunca pode ser fixado administrativamente. Nestas condições, a relativa precariedade das análises de viabilidade é mais marcada, a amplitude das incertezas mais larga e a sua elaboração mais complexa.

O nosso objectivo não é fornecer soluções ou algoritmos “definitivos a curto prazo” – é propor a reflexão e a crítica como método. E, como a funcionalidade é uma componente necessária da análise, surge, inevitavelmente, uma proposta metodológica que permite quantificar e, mais importante, escalonar o impacto de variáveis parametrizáveis na rendibilidade de um projecto.

  1. Curso de Hidrometalurgia (Hydrometallurgy Course), Scholar Publication for the students in Mining Engineering, F.E.U.P..

1985 Estudo de Viabilidade do Projecto do Complexo Mineiro do Alto Alentejo (Feasibility Study of the Alto Alentejo Mining Complex Project), 20 volumes, 2500 pages, coordenation, main reporter and researcher. Empresa Nacional de Urânio, E.P.
Relatório integrado e abrangente, em 20 volumes, contemplando os principais componentes tecbológicos envolvidos numa futura exploração dos jazigos do Distrito Mineiro Uranífero da Alto Alentejo. Vol. 1 – Introdução e Inserção Conjuntural do projecto; Vol.2 – Síntese do Projecto; Vol. 3 – Trabalhos e Estudos Preliminares; Vol. 4 – Recursos e reservas; Vol. 5 – Planeamento Mineiro; Vol. 6 – Alternativas de Tratamento Hidrometalúrgico; Vol. 7 – Descrição do processo Retido; Vol. 8 – Infraestruturas e Mão de Obre; Vol. 9 – Engenharia Civil; Vol. 10 – Listagem do Equipamento; Vol. 11 – Determinação dos Investimentos Totais; Vol. 12 – Estimativa dos Custos Totais; Vol. 13 – Escalonamento Temporal do Projecto; Vol. 14 – Análise do Mercado; Vol. 15 – Análise Económica do Projecto; Vol. 16 – Análise de Sensibilidade; Vol. 18 – Análise Macroeconómica; Vol. 19 – Estado Radiológico do Ambiente; Vol. 20 – Hipótese de Arranque Escalonado.
1984 Garcia Pereira, Jorge de Sousa, Luís Costa, António Fiúza, Consideração da Envolvente Geológica na Concepção de um Modelo Estatístico do Processo Laboratorial de Lixiviação de Urânio (Consideration of the Geological Environment in the Conception of a Statistical Model for Interpretation of Experimental Leaching Results in an Uranium Ore), 9 pages, Conference of the Natonal association of Engineers (Ordem dos Engenheiros).
O objectivo deste trabalho é a construção de um modelo estatístico de um processo laboratorial de lixiviação de Urânio, relacionando a recuperação em U3O8 com variáveis qualitativas ligadas ao ambiente geológico de cada amostra. De um conjunto inicial de 8 variáveis (presença ou ausência de quartzo, de mineralização expressa, de metamorfismo de contacto, ocorrência de falhas, distância à superfície topográfica, litologia, estado de oxidação, teor do tal-qual) foram seleccionadas, através de uma análise das correspondências, as 5 variáveis não redundantes cuja correlação com a recuperação é máxima. Finalmente foi obtido, por regressão sobre as projecções das modalidades correspondentes a essas 5 variáveis, um modelo simples relacionando a recuperação com as modalidades das variáveis em que estas se apresentam em cada amostra. Com base neste modelo é possível prever, ex-ante, a recuperação a obter num dado ensaio, conhecidas as características geológicas e geoquímicas do minério a submeter ao ensaio. O modelo permite ainda hierarquizar a importância das variáveis e contribuir para a definição de alvos de prospecção.
1984 Fiúza A., Algumas Considerações sobre a Aplicação de Taxas Ad Valorem à Indústria Mineira (Some Considerations about the application of Ad Valorem Taxes to the Mining Industry), Divisão de Estudos Económicos, Planos e Projectos, Empresa Nacional de Urânio. 22 pages.
1983 Henrique Garcia Pereira, Jorge de Sousa, António Fiúza, Luís Costa, Improvement of the Interpretation of Uranium Leaching Tests by the Inclusion of Geological Information, 18th International Symposium on Computer Applications in the Mineral Industries, Institution of Mining and Metallurgy, Pg. 441- 447, England, ISI Web of Knowledge, Times Cited: 0, References: 15

Correspondence Analysis has been applied in the last decade to geological problems and mining planning. An extension of this method, denominated qualitative regression, is used in this paper for the purpose of incorporating qualitative geological information into a black-box model for a Leaching process of uranium ores. This model relates the recovery of the process to a set of relevant qualitative and quantitative “explicative” geological variables, the contribution of which to recovery being also assessed through Correspondence Analysis. This model can be used to identify targets for geological exploration (evaluating their favourability in terms of expected recovery); moreover, it allows the planning of further processing tests, minimizing their number and making them consistent with geological environment of samples delivered to the metallurgist.
1983 Fiúza A., Santo Cordeiro, Freire António, Processing of Low Grade ore at the Cunha Baixa Mine, International Atomic Energy Agency, Technical Meeting in Uranium Ore Processing and Recovery from Non-Conventional Resources, Vienna, 12 pages,
The Cunha Baixa mine is located in the Beira Alta Uranium Province. It has been simultaneously exploited by underground and open pit mining. Relatively large quantities of low grade ore were produced and stockpiled regarding to their future processing by heap leaching. After an experimental phase where the amenability of the ore for leaching was confirmed, it was decided to go into full-scale operation.

The process consists of using the old open pit excavation as the heap leaching site, and the solutions are collected in the underground drifts bellow the pit bottom. Pumping towards the surface is done automatically and uranium is recovered by ion exchange in a fluidized bed. Charged resins are transported to the central processing Plant. Effluents are recycled.

The general infrastructures developed will allow the processing of similar ores from surrounding mines; manpower requirements are minimal.
1983 Fiúza A., Santo Cordeiro, Freire António, In Situ Leaching of Urgeiriça Mine, International Atomic Energy Agency, Technical Meeting in Uranium Ore Processing and Recovery from Non-Conventional Resources, Vienna, 16 pages.
In 1971 The Urgeiriça Mine was considered depleted by classical underground mining. Two years before, experiments begun in order to supply the recovery of the residual ore, in old stopes and in newly breaked blocks, by in situ leaching.

From these experiments sufficient know-how was acquired, allowing for generalization of the process to the whole mine, in a full scale operation.

The general process is described as well as the respective infrastructures. The results obtained up to the end of 1982 are expressed in detail.
1983 Fiúza A.M.A, Determination of Leaching Recovery Functions in a Deposit with Different Regional Behavior, in Economics of Uranium Ore Processing Operations, OECD Nuclear Energy Agency, Paris, 1983, Pag. 105-118.
When submitted to moderate leaching conditions, the residues spectrum of the Nisa ore samples was very large, depending manly on iron grade and depth. Determination of mean recovery functions for project purposes was a difficult task. A statistical study was built taking simultaneously into account the uranium and the iron grade distributions, polynomial regression analysis and the resource distribution as a function of depth. This unusual symbiosis between hydrometallurgy, resource evaluation and the deposit mineralogy proved to be a fairly efficient model.
1983 Fiúza A., Santo Cordeiro, Freire António, Tratamento de Minérios Pobres na Mina da Cunha Baixa (Treatment of Low Grade ores at the Cunha Baixa Mine), Mine Bulletin, Volume 20, Nº 3, Jul-Set, Lisbon.
A mina da Cunha Baixa está localizada na província uranífera das Beiras.

A exploração foi simultaneamente subterrânea e a céu aberto, tendo sido produzidas relativamente grandes quantidades de minério pobre, que foram armazenadas tendo em vista o seu futuro tratamento por lixiviação estática. Depois de uma fase experimental em que a boa aptidão do minério à lixiviação foi confirmada iniciou-se a fase industrial.

O processo consiste na utilização da corta como cuba de ataque, sendo as soluções recolhidas na galeria imediatamente inferior ao fundo da corta. A bombeagem para a superfície é feita automaticamente e o urânio é recuperado por permuta iónica em leito fluidizado. As resinas carregadas são transportadas para a Oficina de Tratamento Químico (OTQ) da Urgeiriça, sendo os efluentes reciclados.

As infra-estruturas criadas permitirão tratar minérios idênticos de minas adjacentes com necessidades mínimas de mão-de-obra.
1983 Fiúza A.M.A., Preliminary Optimization of Ore Grades for Alternate Exploitation and Processing Methods, in Economics of Uranium Ore Processing Operations, OECD Nuclear Energy Agency, Paris, 1983, Pag. 119-130.
Once a deposit has been studied by statistical methods of uranium resource evaluation and before advanced economic studies can be worked out in detail, it is worthwhile, particularly if alternative exploitation and processing methods are to be considered, to analyze ore reserves as a function of their grade.

The methodology proposed consists of the simultaneous application of tonnage-cut-off grade curves, mean grade – cut-off grade relations, and profit equations, which allow the definition of economic and recovery functions that may be used for preliminary optimizations.

1982 Projecto de Nisa - Balanços Mássicos, Energéticos e Dimensionamento Prévio do Equipamento, (Nisa Project – Materials and Energy Continuity and Previous Design of Main Equipment), Empresa Nacional de Urânio, 250 pages..
Comparam-se três circuitos alternativos para a primeira fase do tratamento hidromineralúrgico do minério de Nisa. O primeiro circuito compreende britagem, granulação, moagem em via húmida em moínho de barras, lixiviação à temperatura ambiente e separação sólido-líquido (S.S.L.) em 5 espessadores-decantadores em contracorrente. O segundo circuito distingue-se do primeiro pelo facto de a lixiviação ser efectuada a 80ºC, o que exige o dimensionamento adicional de um sistema gerador de vapor. No terceiro circuito a moagem é feita a seco em moínho semi-autogéneo, com aeroclassificação em ciclones, calcinação em forno de leito fluidizado, seguido de lixiviação à temperatura ambiente e S.S.L. num circuito idêntico ao já anterioremente referido. Apresentam-se os balanços mássicos e energéticos e faz-se um dimensionamento preliminar de todo o equipamento principal envolvido, bem como do equipamento auxiliar intermédio de armazenagem. Calculam-se os consumos unitários de reagentes, de utilidades e de energia.
1981 Análise estatística do comportamento do minério de Nisa face à lixiviação (Sytatistical Analysis of the Behaviour During Leaching of the Nisa Ore), E.N.U. – Empresa Nacional de Urânio, E.P., 142 pages.
O minério de Nisa da zona superficial do jazigo apresenta rendimentos de lixiviação baixos devido à existência de associações refractário urânio-limonites. Nas zona reduzida do jazigo tal não deveria acontecer devido ao facto de o ferro existir na forma de sulfuretos. Seleccionaram-se 100 amostras do jazigo pertencentes às zonas oxidadas, reduzida e de transição e foram submetidos a ensaios de lixiviação nas mesmas condições. Analisou-se por regressão o comportamento das amostras em cada uma de 10 classes definidas pela sua profundidade. Dessa análise resultou a consideração de três classes de comportamento consoante a profundidade da amostra. Em seguida considera-se cada uma das populações como bi-log-normal, e fez-se a sua comparação. Conclui-se que as populações sob o ponto de vista de teores em urânio e ferro são estruturalmente idênticas, ou seja uma população bi-log-normal, sem correlação entre as distribuições de urânio e ferro, que são portanto aleatórias uma relativamente à outra o que significa que a diferença de comportamento apenas pode ser imputada a diferente composição mineralógica. Calcula-se em seguida modelos de previsão da recuperação por regressão linear múltipla para cada uma das três classes de minério e estima-se a distribuição de teores em profundidade. A associação destes dois resultados permite prever os rendimentos em função da localização da amostra e estimar valores médios globais para o jazigo.
1979 Cordeiro Santo, António Freire, Matos Dias, António Fiúza, Cesário Coelho, Sales Machado, Valorização dos Recursos Uraníferos Nacionais (Valuation of National Uranium Resources), Conference of the National Engineer Association (Ordem dos Engenheiros), Porto. 77 paginas.
Analisam-se as diversas fases desta indústria extractiva e integram-se num cenário global, dissecando algumas das múltiplas relações existentes entre as diversas etapas. É dado um realço particular à selecção dos métodos de desmonte. Na parte final analisa-se em grande detalhe a componente económica, pois que a parametrização da gestão destes recursos escassos constitui um problema de âmbito e de interesse nacional.
1978 O Problema da Calcinação no Tratamento do Minério de Nisa (The Problem of Roasting in Processing the Nisa Ore), Junta de Energia Nuclear, Direcção Geral dos Serviços de Prospecção e Exploração Mineira, Lisboa, 140 pages.
O minério uranífero do jazigo de Nisa apresenta em condições normais de lixiviação rendimentos de extracção da ordem de apenas 80%. A recuperação pode ser substancialmente melhorada, obtendo-se recuperações da ordem de 90%, fazendo uma ustulação prévia do minério. A explicação reside no facto que a componente refractária à lixiviação modera – uma associação entre o urânio e minerais de ferro (essencialmente goetites e limonites) – é destruída pela ustulação ficando o urânio disponível para dissolução. Neste trabalho comparam-se três circuitos de tratamento de minérios: Circuito 1 – Moagem em moínho de barras em via húmida, lixiviação em condições moderadas à temperatura ambiente e separação sólido-líquido em DCC; Circuito 2 – Moagem autogénea ou semi-autogénea a seco, lixiviação em condições moderadas e SSL em DCC; Circuito 3 – Idêntico a 1 mas utilizando na lixiviação ácido concentrado e uma temperatura de 60ºC


  1. Auto-Evaluation Report for the National Council for Evaluation of High Education (CNAVES) – Report Referring to the period 1996 - 2002, Text submitted to the Foundation of Portuguese Universities, Coordination and main author.

  1. Second Process for Accreditation at the National Association of Engineering (“Ordem dos Engenheiros”), Period 2002-2008, Coordination and main author.

  1. Report on the Preliminary Research about the contamination of the subsoil at Petrogal Refinery in Leça da Palmeira: Generic study about the dispersion and intensity of subsoil contamination with petroleum products: Preliminary characterization of the local subsoil and its main properties, Main properties of the contaminants that present higher potential environmental risk, treatment and interpretation of data acquired in previous sampling, Sampling done in December 2000 – Analysis and interpretation, measures for Mitigation and suggestions future work. 137 pages, December de 2000.

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1985 Feasibility Study for the Alto Alentejo Mining Complex Project, 20 volumes, 2500 pages, coordination, main reporter and researcher.
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