Galvanised steel atmospheric corrosion is a complex multifactorial phenomenon that globally affects many structures, equipment, and sectors. Moreover, the International Organization of Standardization (ISO) standards require specific pollutant depositions values for any atmosphere classification or corrosion loss prediction result. The aim of this research is to develop predictive models to estimate corrosion loss based on easily worldwide available parameters. Experimental data from internationally validated studies were used for the data mining process, basing their characterisation on seven globally accessible qualitative and quantitative variables. Self-Organising Maps including both supervised and unsupervised layers were used to predict first-year corrosion loss, its corrosivity categories, and an uncertainty range. Additionally, a formula optimised with Newton’s method has been proposed for extrapolating these results to long-term results. The predictions obtained were compared with real values using Euclidean distances to know its similarity degree, offering high prediction performance. Specifically, evaluation results showed an average saving of up to 16% in coatings using these predictions. Therefore, using the proposed models reduces the uncertainty of the final structures state by predicting their material loss, avoiding initial over-dimensioning of structures, and meeting the principles of efficiency and sustainability, thus reducing costs.
Paste and thickened tailings (P&TT) technology has important advantages not only from the safety point of view, but especially from the environmental point of view. The objective of this paper is to prove that this technology is a real sustainable alternative that can be evaluated using life-cycle analysis (LCA) methodology. P&TT has emerged in recent years as an alternative for the treatment and disposal of mine waste. It involves thickening the tailings (a mix of process water and waste solids obtained after the process of separating the gangue of an ore) to a higher solid content, recovering the water, and recycling it back to the process. The volume of the final waste once it has been thickened is smaller and requires less storage capacity. Conventional tailings disposal has some important disadvantages such as poor water recovery, high volume storage requirements, the need for containment structures like basins or dams (which can present stability and safety issues), and lower rehabilitation potential. Thickening technologies applied to tailings, in order to reach solid concentrations over 50%, are a real alternative to traditional disposal techniques. Scarcity of water and increasing demand for higher recycling rates can be partially solved, pollution and seepage problems are avoided, smaller containment facilities are required, and footprint is reduced due to smaller land needs, even allowing partial rehabilitation while the mine is still under operation.
Thickening tailings until they reach a paste-consistency configuration is a process involving many factors. Lab scale work is required prior to studying the feasibility of paste thickening technologies for a given tailings. The global objective is to determine if a representative sample of non-thickened tailings can be engineered at laboratory scale to make paste; this work and its results will help determine the feasibility of the thickening process and the potential paste characteristics at industrial scale. This document aims to justify the need for this lab scale work and to provide information regarding lab scale paste thickeners by presenting the experiences obtained with an experimental lab-scale thickener.Studying the feasibility of a paste and thickened tailings (P&TT) alternative for a mine requires different types of laboratory and pilot scale tests. Many parameters and factors will affect the viability of these technologies for a given case. If we examine the most widely accepted theory, it seems that global design should flow 'upstream', starting from the storage area characteristics, stepping back to the piping requirements, and finally defining the thickening process to suit the required characteristics of the underflow.The characteristics of tailings are probably the most important of the factors affecting the viability of the whole process. Location determines the climate, and especially the geological and mineralogical properties of the deposits, but tailings should not be considered as a natural material. They are a waste product of the mining process and are affected by several other parameters: the process used to separate the gangue from the ore, the chemicals added during these processes, the characteristics of the water used, etc. Even during the lifetime of a mine, the tailings characteristics may change due to evolution of the mineral grade and the associated beneficiation process.All these arguments make tailings processing not only site dependant, but also time dependant. The design of a P&TT process to thicken the waste of a mine requires a strong phase of prior research to determine its feasibility; not all tailings are amenable to being 'engineered' to reach paste consistency. Even if they are, there are several parameters that can be modified, such as additives, dosage, solids percentage, rheological properties, etc.Thickener design should adapt to these requirements. However, few reference documents with procedures to design these pieces of equipment are available. It seems clear that producing paste at lab scale is imperative in order to have a first idea of how the tailings will behave after being thickened. In order to do this, having a bench scale thickener seems to be a good alternative. Static settling tests do not seem to resolve the need to determine underflow solid concentrations and overflow water characteristics. There is no reference bibliography to construct pilot units; in this study, an experimental column of 9 cm diameter is tested, operating in batch mode, providi...
In August 2014, the international standard ISO 14046:2014 'Environmental management-Water footprint-Principles, requirements and guidelines' (International Organization for Standardization [ISO] 2014) was released. This is the first version ever published on water footprint, and therefore an important milestone for all environmental activities related to water management. The issue of water and its management has become increasingly central to the global debate on sustainable development. This interest has been driven by growing water demand, increasing water scarcity in many areas and/or degradation of water quality. This drives the need for a better understanding of water related impacts as a basis for improved water management at local, regional, national and global levels. It is therefore desirable to have appropriate assessment techniques that can be used in an internationally consistent manner. One of the techniques being developed for this purpose is the water footprint assessment (ISO 2014). Water and mining have always had a close connection because most mining and mineral processing operations require water, often in large amounts (Rowe 2012). Mining activities can contaminate surface and groundwater and demand great amounts of water, especially froth process used as a method of minerals separation. There are some minerals such as coal, cyanide or bauxite that can severely affect freshwater resources. Moreover, closure stage requires special treatments because of significant long-term environmental liabilities-they must be pumped and treated indefinitely to prevent contamination of surface and ground waters (Hendrix 2012). Despite of the fact that mining represents a very small fraction of the total world's water demand, its impact on local resources surrounding mine sites can be significant. The problem is that mining operations cannot be relocated, making the sector susceptible to changing local water availability (Barton 2010). Paste and thickened tailings technology is nowadays a proven solution for one of the biggest environmental impacts of mining activities: tailings disposal. Among the various drivers that this technology has, water is probably one of the most important, not only from an environmental perspective but also from an economic one. This paper applies the methodology proposed by the Water Footprint Network International and later published as an ISO norm, to assess the differential Water Footprint of two scenarios, conventional tailings management and its alternative process, paste and thickened tailings. Satisfying the demand for higher living standards is heavily dependent upon mineral products from expanded mining activities (Society for Mining, Metallurgy and Exploration, Inc. [SME] 2012). On the other
According to the database compiled by the US Commission on Large Dams (USCOLD) and completed later by the International Commission on Large Dams (ICOLD) and the US Environmental Protection Agency (EPA), there have been two or more major tailing dam failure incidents per year between 1970 and 2000, proving that these catastrophic failure events are not rare occurrences. Paste and thickened tailings (P&TT) technology has emerged in recent years as a promising technique to avoid dam incidents. Due to the low water content of the P&TT, the potential for liquefaction is reduced drastically in comparison to conventional tailing dams. This is one of the major advantages of the technology, alongside the volume reduction and the absence of bleed water. However, paste also has some drawbacks such as higher energy consumption and extra equipment requirements. Due to these advantages and drawbacks, a set of different tools is required to assess the feasibility of a paste facility at a specific mine. Among these tools, those related to risk become important since one of the major advantages of paste is related to this dimension. Thus, selecting the right tool for analysis is a key factor in the decision-making process that may lead to the selection of P&TT as an alternative to conventional tailings storage. According to the AS/NZS 4360:2004 'Risk Management' (Standards Australia 2004), developing a risk assessment involves a three-stage process: identify, analyse and evaluate all the risks involved. The best tool to provide structure for these stages is a failure modes and effect analysis (FMEA) of the tailings system. In the present work, a general comparison between P&TT and conventional tailings storage has been made in terms of risk, using a FMEA based on a classification of likelihood and consequences in a semi-quantitative risk assessment. All risks for stages from the concentration plant onwards are considered for each scenario, in two different categories: environmental and public safety. Paste and thickened tailings technology has more risks classifying as low to moderate than conventional tailings and has less risks classifying as moderate to high area. These results can be used as an indication of the sustainability of P&TT disposal in terms of risks. Although the goal of the study is to make a general comparison not applied to any specific mine, it can also be used as a methodology or template for a risk assessment for any existing installation.
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