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By José Antonio, Silva Souza, Luis Alves Venancio, Emanuel Negrão Macedo, Antonio Ernandes M. Paiva

"The production of alumina from bauxite using the Bayer process generate 1.25 ton of the residue known by red mud and 460 kg of CO2 per ton of alumina.The direct use of exhaust gases from the alumina refineries to react and neutralize the bauxite residue may allow a double gain: open a wide range of new applications for bauxite residue reducing the reactivity of red mud and sequester approximately 15% or 67 kg of CO2 per ton of alumina.This paper shows the reaction of a suspension of bauxite residue-water with a simulation of the calcinator exhaust gases of the refinery. The influence of the temperature and the ratio water red mud is also analyzed.2 IntroductionThe production of millions of tons per year of alumina around the world generates around 1.25 tones of the residue known as red mud and 0.4 ton of CO2 per ton of alumina . The vast majority of the red mud is stored in large sealed lakes. Due to the high reactivity is considered dangerous and currently there is no operating process capable of reuse all the material at any refinery. These lakes after filled of solid material eventually have the surface revegetated. Otherwise will need monitoring for decades and remain as an environmental passive. The search of a industrial process that combine the reduction of the CO2 emission and the reduction the pH of the red mud opening the possibility of use in large scale in a economically viable way is the main objective of this work.The use of the exhaust gases of the refineries to neutralize the bauxite residue may allow a double gain: Open a large array of new applications for the residue with the reduction of its reactivity and sequester million of tones of CO2 plus other gases like SO2 [7] and NOx.This project main objective is to study the reaction of the CO2 with the Bayer process residue in order to obtain the basic parameters to design an equipment capable of process this reaction on a pilot scale. With this objective compositions of red mud on spray were processed with flow of gas containing CO2 at different temperatures and with concentration similar to the exhaust gases of the calcination process of the refineries. With the results, basic concepts of a pilot scale equipment were evaluated.A revision of the work already done on this type of residue were done [3, 9, 10]. Alternatives and potential barriers on chemistry and environmental fields were discussed. With the objective of industrial application the potential use of these materials were evaluated through the pH control, mass balance and x-ray diffraction."

Jan 1, 2010

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Masanori Harata

A fundamental study was conducted on a new process for producing scandium (Sc) metal or aluminum-scandium (Al-Sc) alloy by the calciothermic reduction of scandium oxide (Sc2O3). In this study, aluminum (Al) and calcium chloride (CaCl2) were used as the collector metal and flux for the reduction, respectively. A mixture of Sc2O3, Al, and CaCl2 in a tantalum crucible was placed inside a stainless steel reaction container, and the feed mixture was reacted with calcium (Ca) vapor at 1273 K for 6 h. After the reduction experiment, the reaction product (CaO), CaCl2 flux, and excess Ca reductant were removed from the obtained alloy sample by leaching with an aqueous solution. The formation of Al3Sc in the Al matrix phase of the alloy was confirmed by X-ray diffraction (XRD) and electron microprobe analysis (EPMA). This result indicates that Sc2O3 was successfully reduced to metallic Sc and alloyed in situ to form liquid Al-Sc alloy during the reduction. When Al was not used in the reduction experiment, a complex oxide (CaSc2O4) was formed, and the reduction was incomplete. This study demonstrates that the Al-Sc alloy can be directly produced by calciothermic reduction using CaCl2 flux and Al collector metal.

Jan 1, 2006

By Florian Kongoli

While calcium ferrite slags have been successfully used in continuous copper converting for the last 30 years, ferrous calcium silicate slag was proposed about 8 years ago as an additional alternative for copper smelting. Although both slags are normal extensions of each other their phase relations have not been completely clarified. In this paper the liquidus relations of both slags have been quantified at various areas that cover both of them. The existing experimental data have been first reviewed and discussed in relation to the solidification procedure. An original physical model is then used to predict various diagrams of the liquidus surface of both slags. It is shown that the ternary liquidus diagrams normally used for FeOx-SiO2-CaO system are not suitable for industrial slags. The new model diagrams of Fe/CaO versus SiO2 and Fe/SiO2 versus CaO as well as Fe/CaO versus Temperature and Fe/SiO2 versus temperature are proven to be much more convenient for ferrite and ferrous calcium silicate slags. Based on these diagrams the effect of SiO2 and CaO on the melting temperature is quantified. The effect of Cu2O is also quantified through the model. Some Fe/CaO versus Cu2O and Fe/SiO2versus CaO at various copper contents are predicted and the results show good agreement with the experimental data. It is also shown that in the presence of liquid copper, Cu2O is dissolved in the slag depending on the oxidation degree of the system and might lower the liquidus temperature. Some discussions are also presented taking into account plant observations and important conclusions are drawn for copper smelting and converting

Jan 1, 2006

By S. Fitzel

The Betts process for electrorefining of lead has been in operation since 1902 in the Trail Operations Metallurgical complex. The Betts process allows production of high purity lead in a single electrochemical step. Process improvements and plant expansions have taken place over the many decades of operation of this process which has proven to be robust, flexible, and capable of successfully treating a large range of anode bullion compositions. This paper reviews the history of the Betts lead electrorefining process, the innovations and quick industrial adoption of new discoveries that took place at the end of the nineteenth century. The process was first implemented in Trail Operations and integrated very well with metallurgical needs then and now.

By E. V. Verhoej

The proposed EU directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment promotes the substitution of lead in consumer electronics to reduce emissions from lead in the end of life phase. In this paper, the consequences of substituting lead in solders is assessed using the Eco-Indicator-99 method for the examples. The base metal production system is considered as an interconnected network modeled dynamically in Simulink 4 and Matlab 6 (Mathworks Inc 2000), where the recovery and production of metal components of the assessed product partially overlap. This approach requires global modeling of metal production processes and mass balances and resulting allocation choices. It also reveals the susceptibility of LCA scores to different choices in the modeling and data availability and uncertainty. Besides the comparison between lead-free and lead-containing solders, other side effects are revealed. Lead is carrier material for the recycling and production of many co-elements in the interconnected production and recovery system. Substitution may have adverse effects such as temporary shortages of other connected metals that are often not considered in normal LCA assessments, thus leading to erroneous results. The suggested approach provides directions for including these extemal effects and for further assessment of the environmental effects of substituting lead. This paper shows that in order to assess the environmental aspects of metallurgy, dynamic modeling of the total system is required based on the fundamental thermodynamics in each metallurgical reactor, the basis of this dynamic model. With this the true environmental impact of metallurgy can be explained. In the case of lead free solder, it is shown that the mining of substitutes has a very much larger impact.

Jan 1, 2003

By E. V. Verhoef

The proposed EU directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment promotes the substitution of lead in consumer electronics to reduce emissions from lead in the end of life phase. In this paper, the consequences of substituting lead in solders is assessed using the Eco-lndicator-99 method for the examples. The base metal production system is considered as an interconnected network modeled dynamically in Simulink 4 and Matlab 6 (Mathworks Inc 2000), where the recovery and production of metal components of the assessed product partially overlap. This approach requires global modeling of metal production processes and mass balances and resulting allocation choices. It also reveals the susceptibility of LeA scores to different choices in the modeling and data availability and uncertainty. Besides the comparison between lead-free and lead-containing solders, other side effects are revealed. Lead is carrier material for the recycling and production of many co-elements in the interconnected production and recovery system. Substitution may have adverse effects such as temporary shortages of other connected metals that are often not considered in normal LeA assessments, thus leading to erroneous results. The suggested approach provides directions for including these external effects and for further assessment of the environmental effects of substituting lead. This paper shows that in order to assess the environmental aspects of metallurgy, dynamic modeling of the total system is required based on the fundamental thermodynamics in each metallurgical reactor, the basis of this dynamic model. With this the true environmental impact of metallurgy can be explained. In the case of lead free solder, it is shown that the mining of substitutes has a very much larger impact.

Jan 1, 2003

By M. Kawakami

In relation to the designing of a new-type blast furnace, the reaction of carbonaceous materials with C02 is expected to occur at as low temperature as possible. In order to get a highly reactive carbonaceous material at low temperature, the reaction kinetics was investigated by measuring such quantities as the reaction rate from weight loss, the amount of CO adsorption and specific surface area by BET method. The reaction rates were large in the order of the Bintyo char, metallurgical coke, graphite and glassy carbon. If the rate was converted to the rate per unit area, however, those of the Bintyo char was smaller than that of graphite. Thus, it is suggested that the rate of the Bintyo char is influenced by the pore diffusion of C02. The rate had a positive relation with the amount of CO adsorption, showing that the rate determining step would be the desorption of CO from the active side on the surface. The rate independent of surface area was derived, combining al\ the obtained data.

Jan 1, 2003

By Riyad N. Ahmad-Bitar, Shadia J. Lkhmayies

"CdSi-xTex thin films were prepared by first producing CdS:In thin films by the spray pyrolysis (SP) technique and then annealing the films in the presence of Te vapor in nitrogen atmosphere. X-Ray diffraction (XRD) measurements showed that the films are polycrystalline with the wurtzite structure. Transmittance measurements were recorded at room temperature in the wavelength range 400-900 nm and used to deduce the absorbance. The first derivative of the absorbance was calculated and used to find the values of the bandgap energy, where more than one bandgap was obtained for each film. These results show that the films are inhomogeneous or the composition differs with location. The photoluminescence (PL) was recorded at T = 60 K and a deconvolution peak fit was performed for each spectrum. The results of the PL spectra are consistent with those obtained from the first derivative and confirm the inhomogeneity of the films.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The CdS/CdTe interface plays an active role and a detailed knowledge of its properties is crucial for thorough understanding of the device. High efficiency devices have been obtained in spite of the large lattice mismatch (9. 7%) between hexagonal CdS and cubic CdTe. Interdiffusion at the CdS/CdTe interface is considered to affect the performance of the devices [1]. The formation of a mixed crystal or a graded layer at the interface causes a reduction in the lattice mismatch at the CdS/CdTe junction [2] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [3, 4].The objective of this work is to investigate the transmittance, photoluminescence (PL) and structure of CdSi-xTex thin films prepared by annealing the spray-deposited CdS:In thin films in the presence of tellurium vapor. X-ray diffraction (XRD) was used for exploring the structure. Transmittance is used to deduce the absorbance where its first derivative was used to find the bandgap energy which varies with composition. The evolution of the PL spectra as functions of tellurium concentration was evident and it confirmed the inhomogeneities of the films."

Jan 1, 2011

By Xianzhong Hu, Qingbo Yu, Qin Qin

"Oxy-fuel combustion is one promising option among different CO2 capture technologies. The object of this work is to show the effect of CO2 dilution on the laminar flame speed, flame structure and reaction pathway for methane oxidation at O2/CO2 atmosphere. In this paper, kinetic simulations were made using CHEMKIN with GRI-Mech 3.0 mechanism, which was validated by experimental data of laminar flame speeds. The reaction pathway of CH4/O2/CO2 mixture was derived from reaction flow analysis. Results showed that CO2 decreased the flame speeds, lowed concentration of major intermediates and increased flame thickness. The major chemical pathways of CH4 to CO2 have not changed at O2/CO2 atmosphere comparing with O2/N2 atmosphere, but contributions to major intermediates formation from each related elementary reaction have changed a lot. In addition, the secondary chemical pathways of CH3 oxidation became different at O2/CO2 atmosphere.IntroductionNowadays, as the global economy is developing fast and the pollutant levels (especially global warming gases) are increasing, a lot of researches are focusing on new technologies which can cut greenhouse gas emissions [1]. New technologies have been developed, such as high Mild combustion, flameless combustion and Integrated Gasification Combined Cycle (IGCC) technology. Oxy-fuel combustion using carbon dioxide as dilution of oxygen is considered as a promising approach for reducing CO2 emission. The properties of CO2 in flue gas are different from N2 in air. On one side, the transport, thermal and radiative properties of CO2 are different from N2 in air. On the other side, CO2 is not inert but directly participates in chemical reactions and recent researches [2-5] also present the chemical effects of CO2 on oxy-combustion. For these differences above, the characteristics of oxy-combustion are not alike with traditional combustion. It is necessary to develop the investigation of oxy-combustion.In all combustion processes, laminar flame speed is an important parameter, which links to combustion behavior. Analysis of this parameter can provide a better understanding of the effect of CO2 dilution in the process of oxy-combustion. Several investigations of laminar flame speeds of oxy-fuel flame have been improved, including experimental measurements and numerical computations. A.A.Konnov et al. measured the flame speeds of oxy-methane and oxy-ethane mixture using the heat flux method with a flat burner [6-8]. V. Ratna Kishore et al. used heat flux method to measure the adiabatic laminar flame speeds of hydrogen [9] and H2/CO mixture [10]. Adiabatic laminar flame speeds of hydrogen in O2/CO2 atmosphere are much smaller than in O2/N2 or in O2/Ar. The burning velocity of H2/CO mixture decreased with increase in CO2 content in mixture. Jeongseog Oh et al. [11] used Bunsen flame to measure the laminar flame speeds of premixed oxy-methane mixture with angle methods in atmospheric condition (300k, 1atm). The results were SL=29.1cm/s and SL=29.5cm/s respectively derived from oxy-methane from CH* images and Schlieren photos."

Jan 1, 2014

By T. B. Braun

Cathode contamination is the principal factor affecting the quality of electrorefined copper. It is commonly accepted that annealability is unfavorably affected by the following elements, in decreasing order of adverse effect: tellurium, selenium, bismuth, antimony, and arsenic. Silver in cathodes has importance as it represents a nonrecoverable loss of silver to the refinery. Mechanisms for the contamination of cathodes by these elements are examined and the effect of operating variables on contamination, including anode composition, electrolyte composition, electrolyte temperature, addition agent practice, and electrolyte discard rate, are discussed.

Jan 1, 1976

By T. Yoshida

The Ni-MH (nickel metal hydride) rechargeable battery was developed several years ago. Its higher electrochemical capacity and greater safety compared with the Ni-Cd rechargeable battery have resulted in very rapid Increase in its production. The Ni-MH rechargeable battery consists of Ni. Co and rare earth metals, so that recycling is important to recover these valuable mineral resources. In this study. a basic recycling process for used Ni-MH rechargeable batteries has been developed, in which the Ni. Co and rare earth elements are recovered through a combination of mechanical processing and hydrometallurglcal processing.

Jan 1, 1995

By S. Sugiyama, M. Kiuchi

"New metal working processes, such as the mashy-state mixing, mashy-state forging, mashy-state rolling and mashy-state extrusion are developed and applied to manufacture the so-called particle reinforced metals, fiber reinforced metals, particle reinforced cladding metals and so forth. These metal-ceramics composites are made of metal sheets, metal powders, ceramics particles and ceramics fibers. The mashy-state processes are also used to work those composites into bars, wires, tubes, plates, sheets, machine parts and other products. The working conditions necessary to manufacture sound composite products are clarified and the mechanical properties of the products are investigated. Through the investigation, it becomes clear that the mashy-state processes are useful and effective to manufacture metal-ceramics composites. It is al so known that these processes may be applied in various ways to development of new metal matrix compounds. IntroductionThe so-called metal-ceramics composites and processes to manufacture them are now being widely investigated in order to comply with increasing demands for new materials with novel and excellent mechanical properties and functions. The metal-ceramics composites are expected to have superior characteristics with respect to the elastic modulus, hardness, anti-wear resistance, high temperature strength and other mechanical properties to those of conventional metallic materials.The present authors ha v e been investigating into new metal working processes which are based upon the characteristics of metals and their alloys in the mashy-state. In the mashy-state, the metal (or alloy) includes both of the solid and liquid components. According to the fact that the partial melting takes place and the liquid component usually exists at grain boundaries, the metal in the mashy-state has quite different mechanical properties from those of the metal in the solid-state. Because of that the bonding force among grains is very weak due to the partial melting occurred at grain boundaries, the mashy metal has distinctively low flow-stress and high deformability. The mashy metal splits into grains or particles and sticks to others very easily. It is so soft as to be stirred up just like a lump of sherbet, but it is sufficiently viscous to be mixed up with other materials, such as ceramics particles and ceramics short-cut fibers."

Jan 1, 1988

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of Ti02 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the Ti02 film in H2S or CS2 gas at 1273 K for 1 hour, the surface atomic structure was changed. Furthermore, the Ti/TiO2 film was successfully prepared by the subsequent ablation of Ti and TiO2 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By Shenghui Guo, Jian Chen, Hongbo Zhu, Jinhui Peng, Linqing Dai, Qianxu Ye

"Response surface method (RSM) based on mono-factor experiment was applied for the process optimization of sintering of chromite fines by microwave. In RSM analysis, effects of binder addition amount, sintering temperature and holding time on the compression strength and shatter strength of the sinter were examined. Results showed that the optimal values of the above parameters were determined as follows: binder addition amount of 1.90% (in mass), sintering temperature of 1153? and holding time of 16 min. Under the optimized conditions, the compression strength was 11155.8? and shatter strength was 95.6849%. The results show that the process was optimized by response surface methodology is stable and feasible, and provide a new way for sintering of chromite fines.IntroductionChromite ore is the main feedstock for ferrochrome, and ferrochrome can be used as steelmaking additive to produce a variety of great strength, corrosion resistant and oxidation resistant special steel, which can be widely used in the aerospace, automotive, shipbuilding, military departments[1], and it has important strategic significance. At present, among the annual world's mined chromite the number of lump ore continues to diminish with its price rising sharply, while the proportion of ore fines been always increased, and the difference in prices between ore fines and lump ore is growing[2]. Despite the low price of chromite fines, and its rich in resources, it can be only used for ferrochrome smelting after agglomeration. Thus manufacturing blocks by using cheap chromite fines is an effective measure to reduce the cost of ferrochrome production and use the chromite resources[3]."

Jan 1, 2013

By Fatbardha Osmani, Skender Osmani

"A system analysis of the resource and environment management (water, energy etc) starts from its definition. Unfortunately, there is not a unique semantics of the mentioned concept. On these circumstances, in this paper the following issues are presented: 1.A short view on the existing concepts of management. 2.A new definition on the concept of management. It is considered as a complex and rational activity on human and natural resources ,environment etc, which starts from a analysis of infrastructure ,technology , etc, mission , alternatives , project etc. and ends to an optimal output. Basing on this definition, the management has two principal components: strategy and policy. The strategy is referred as a blue print program (the same definition as in Game Theory), which contains all the contingency alternatives. , while the policy is referred as a strategy applied into practice. The strategy is the first , while the policy is the second one. The best alternative of a policy is the project, Each strategy has one and only one project. The mentioned definition erases the differences between concept of policy and politics. Each strategy has its alternatives ,the next has its sub strategy and so on, i.e. whatever are going to be the strategy, there are a hierarchy composed by sub strategies up to the simplest strategies applied by a single individual (human beings or robots). The strategy objectives are necessary and sufficient conditions for its realization i.e . the strategy is an optimal activity, in which all resources are integrated and processed . Several strategies could be joined into one( for example the surface water strategies of the Balkan countries) . In this view, the strategy could be globalized into optimal way basing on different criteria’s as social, economic, environmental, their risks and effectiveness etc. etc An example from the water management illustrates the mentioned concepts."

Jan 1, 2008

By T. Nakamura

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of TiO2 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the TiO2 film in H2S or CS2 gas at 1273 K for I hour, the surface atomic structure was changed. Furthermore, the Tirri02 film was successfully prepared by the subsequent ablation of Ti and Ti02 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By O. Nakai

In the copper electrorefining process, the quality of the starting sheet is one of the basic factors for producing high quality copper cathodes. A highly automated and advanced facility for the production of copper starting sheets was constructed at the Toyo Copper Refinery in 1992, bringing various improvements into an automatic stripping system using stainless steel mother blanks. In 1998, the refinery expanded the tankhouse by another 128 commercial cells, and introduced 64 polymer concrete cells in a first stage conversion. As a result, the Toyo Copper Refinery now has the capacity to produce 103,200 t/y of cathode copper. Construction has led to great improvements in the materials handling facilities and computer associated short-circuit detection technology. This report summarizes the improvements made in the quality of the cathodes and in plant productivity.

Jan 1, 1999

By Christian Redl

"The Lattice Boltzmann Method (LBM) solves fluid dynamics problems based on a discrete mesoscopic approach. It is based on the Lattice Boltzmann equation which is a special discretisation of the continuous Boltzmann equation. Its principle advantage is that it can handle complex physical phenomena (like interaction between different components and surface effects), complicated boundary and initial conditions very well, free from many gridding and stability constraints that plague conventional numerical methods used for fluid flow simulations. Complex structures like porous media can be resolved directly. The LBM algorithm has a simple structure and acts locally, which is favourable for parallel computing. Its potential for metallurgical process simulation is demonstrated in the present study which is concerned with the simulation of the fluid flow in a copper winning electrolysis cell. The electrolyte is modelled as the carrier fluid and the oxygen is considered via a so called active scalar equation. The modelling of buoancy, momentum exchange and the free surface requires special effort. The results of the simulation are validated against experimental data obtained by Laser-Doppler-Anemometry. Despite the simplifications made, good agreement between the simulation and the experiments was found.IntroductionThe hydrodynamics in an electrometallurgical cell is a complex, highly non-linear phenomenon. It includes the simulation of a two component system with high density ratio, gravity driven flow and a free surface. A general solution to this problem is currently unknown.The flow field is a result of the combination of various hydrodynamic effects [18]. Metal deposition at the cathode yields in a decrease in the ion concentration, which reduces the density of the electrolyte. At the anode molecular oxygen is formed as a consequence of the oxidation of water molecules. The oxygen is solved in the electrolyte and again the electrolyte density is decreased. Both effects lead to a free upwards directed convective flow, refered to as natural convection."

Jan 1, 2001