Attila Egedy

Eco-friendly copper recovery process from waste printed circuit boards using Fe3+/Fe2+ redox system

The present study aimed at developing an original and environmentally friendly process for the recovery of copper from waste printed circuit boards (WPCBs) by chemical dissolution with Fe(3+) combined with the simultaneous electrowinning of copper and oxidant regeneration. The recovery of copper was achieved in an original set-up consisting of a three chamber electrochemical reactor (ER) connected in series with a chemical reactor (CR) equipped with a perforated rotating drum. Several experiments were performed in order to identify the optimal flow rate for the dissolution of copper in the CR and to ensure the lowest energy consumption for copper electrodeposition in the ER. The optimal hydrodynamic conditions were provided at 400 mL/min, leading to the 75% dissolution of metals and to a low specific energy consumption of 1.59 kW h/kg Cu for the electrodeposition process. In most experiments, the copper content of the obtained cathodic deposits was over 99.9%.

CFD models in the development of electrical waste recycling technologies

Nowadays electrical waste (EW) recycling has become a practical way to provide raw material for new devices. Computer parts such as memory, motherboard or other parts contain large amount of metals from which the recovery of precious metals and copper represents the highest economical potential. With a proper chemical treatment these metals can be efficiently extracted and separated from the actual waste. For this task a specially designed leaching reactor, equipped with a perforated rotating drum, was used. This work is aimed at investigating if computational fluid dynamics (CFD) tools can be efficiently applied to model the chemical reactor used to dissolve the metals from the EW. First a hybrid CFD-compartment approach was developed to describe the dissolution process in the leaching reactor while the CFD models were used to model the hydrodynamics of the process. Based on the detailed model containing momentum and component mass balance the developed simulator could be used to enhance the performance of the existing reactor system. For the modelling studies COMSOL Multiphysics was used as CFD software.

Compartment model structure identification with qualitative methods for a stirred vessel

Solving process design, process optimization, safety analysis and other problems widely relies on mathematical models of the process. To solve problems related to mixing, detailed models such as compartment models or computational fluid dynamics (CFD) models are required. Compartment modelling generally uses four basic compartments: the mixer (M), the distributor (D), the perfectly mixed reactor and the ideal plug flow reactor (PFR). The main modelling tasks using compartment models are defining the structure of the compartment model and determining the parameters of the connections between the compartments. Hence, a qualitative approach was developed to support this identification process. Qualitative methods can be applied to analyse experimental data and to compress the information content of a time series. The primary goal of this study is to present an algorithm based on qualitative analysis that can be used to identify a compartment model structure based on the hydrodynamic measurement data of a stirred reactor.

CFD Modelling and Video Analysis Based Model Validation for a Stirred Reactor

Abstract Investigation of mixing in a stirred tank is an important part of chemical reactor design, optimization or other complex engineering tasks. Computational Fluid Dynamics models are good tools to model the developing flow field in a stirred system; however, an experimental procedure is necessary to validate the model. In our research different geometries were analyzed, and a video based method was developed to validate the CFD simulation results.

CFD-based scale-up and environmental assessment of a rotating drum leaching reactor for WEEE recycling

One of the most challenging engineering tasks is the scale-up of a device. The information transfer between the different scales is crucial because similar yields and conversions should be achieved in a pilot and an industrial-scale device, which were obtained in a laboratory-scale unit. To maintain the same performance, the construction and operating parameters are often changed during the scale-up procedures. Traditionally, dimensionless numbers can be used to calculate the proper operating parameters and sizes for the scale unit. However, a validated computational fluid dynamics (CFD) simulator can be an excellent tool to perform scale-up studies with less time and energy consumption. This work reports a scale-up procedure aimed at supporting the building of a pilot plant-scale leaching reactor, used for the dissolution of metals form waste electric and electronic equipment. Particularly, the process deals with the dissolution of copper which has the second highest economic potential after precious metals. The scale-up studies are based on the validated model of the laboratory-scale reactor. Different construction and operating parameters were tested using CFD simulations. The different cases were evaluated based on conversion (leads to economic potential) and environmental assessment. COMSOL multiphysics will be used as CFD software and MATLAB for conversion and utility calculations and also for environmental assessment.

Kinetic modelling of a pyrolysis gasification reactor

Biomass is of growing interest as a secondary energy source. Biomass could be converted to energy especially by pyrolysis or gasification. Understanding the mechanism and the kinetics of biomass pyrolysis and gasification could be the key to the design of industrial devices capable of processing vast amounts of biomass feedstock. There are multiple reactions describing the decomposition of biomass to gaseous products and it is difficult to identify each of the reactions. Therefore reactions must be simplified; in general well identified reagents and products with different states (feedstock, tar, gas) are used for calculations, instead of using different compounds of real products. In our work real product compounds obtained from pyrolysis were used, and the kinetic constants for biomass pyrolysis and gasification were identified. A laboratory scale reactor was used for the physical experiments containing consecutive fast pyrolysis and gasification stages. The main aim of this research was to create a detailed and validated first principle model for the reactor system. In this study, a compartment modelling approach was used, where all compartments facilitate different reactions (pyrolysis, thermal, and catalytic gasification). With the identification of the model parameters (using PSO algorithm) a stable and validated model was created, which can be used for further optimisation studies. MATLAB was used for the creation of the compartment model, and Particle Swarm Optimisation was used for the kinetic parameter identification.

Experimental Study and Mathematical Modeling of Metals Dissolution from LCD Boards in Na2S2O8 Environment

The current article aims to study the influence of pH, temperature, and oxidant concentrations on the dissolution process of metals from liquid crystal display (LCD) boards in a Na2S2O8 environment. The dissolution rate of metals is enhanced by the decrease of pH and increase of temperature and Na2S2O8 concentration. Based on the obtained results, a reaction mechanism was proposed and the reaction rate parameters (pre-exponential factor and activation energy) were determined. Kinetic analysis of the leaching process was performed in accordance with a shrinking core model. The activation energy was found to be 29,924, 11,871, 22,434, and 38,401 J/mol for Cu, Sn, Ni, and Pt, respectively, in a temperature range of 30°C–75°C, which was also an indication of the combined transport–chemical control. The experimental results were in good agreement with the simulated data and revealed that persulfate solutions are suitable reactants for metals leaching from LCD boards.

Hybrid CFD-Compartment Approach for Modelling and Optimisation of a Leaching Reactor

Abstract The study presents an alternative way to dissolve copper from waste printed circuit boards (WPCBs) using a specially designed leaching reactor and efficient leaching agents. Considering that the leaching reactor is equipped with a perforated rotating drum the fluid flow as well the other related processes (e.g. reactions) can be very complex. Therefore two different model approaches were applied regarding the leaching of copper with FeCl 3 and Na 2 S 2 O 8 as oxidants. The detailed models were validated against multiple measurements performed with the leaching reactor. Then the validated model was used to conduct sensitivity analysis of the operational parameters (reagent concentration, drum revolution speed), and optimal parameter intervals were obtained for the operation of the leaching reactor. COMSOL Multiphysics was used for hydrodynamic modeling and MATLAB for compartment model implementation and sensitivity studies.

Integrated Model Based Framework for Calculation of Geometry Changes in Leaching Process

Abstract In this study an integrated framework is introduced for calculating the geometry changes during the leaching of precious metals from waste printed circuit boards (WPCB). The developed simulator applies hydrodynamic simulation based on a CFD model, while part of the component mass balances and the inducted changes in geometry were calculated in MATLAB. Using a COMSOL Multiphysics-MATLAB interface the two parts were integrated in one framework to calculate the geometry changes. The method and the developed simulator were validated against direct length measurements, and image processing based measurements during a copper solving experiment. The proposed method can be applied for calculating geometric changes of the solid mass.

Application of models with different complexity for a stirred tank reactor

Engineering problem solving such as process design, process optimization, safety analysis, etc.; relies widely on mathematical models of the process. Tosolve various engineering problems various models with different complexity are needed. A stirred tank reactor with a highly exothermic reaction is studied in this work, because in the modern chemical technologies mixing is one of the most important operations, and stirred reactors are widely used in industrial applications. The stirring system of a mixed tank is always an important aspect of the design, because the involved processes (such as reactions, heat and component transport) usually requireproper contact and homogeneity of the existing phases. For the suitable homogeneity the design and the size of the moving parts are also important problems. In certain situations attachment of static parts to a stirred tank (such as baffles) may havean important effect too. The primary goal of this study is to create models with different level of complexity and determine which model is the best suited for solving different engineering tasks such as process design, scale-up, or optimisation. etc. To determine which model fits best for a problem, mathematical models were created and compared to find out, how the information can be extracted from these models and be applied to solve engineering problems. Three types of models have been developed: perfectly mixed reactor model, compartment model, and Computational Fluid Dynamics (CFD) models withdifferent dimensions. The reaction of hydrogen peroxide with sodium thiosulphate in a continuously stirred tank reactor is analysed as a case study. The perfectly mixed vessel models and compartment models were solved in MATLAB/SIMULINK program package. The CFD models were implemented in COMSOL Multiphysics.