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Article
Publication date: 14 August 2007

G.A. Sheikhzadeh and M.A. Mehrabian

The purpose of this paper is to apply the numerical methods to study the heap leaching process in a bed of porous and spherical ore particles. This study is performed in…

Abstract

Purpose

The purpose of this paper is to apply the numerical methods to study the heap leaching process in a bed of porous and spherical ore particles. This study is performed in two stages: first, modeling the leaching process of a soluble mineral from a spherical and porous ore particle to obtain the distribution of mineral concentrations, leaching solvent concentration and dissolved mineral in the particles (the particle model), and second, modeling the heap leaching of the mineral from a porous bed consisting of spherical and porous ore particles to obtain the distribution of mineral concentrations, leaching solvent concentration and dissolved mineral in the bed (the bed model).

Design/methodology/approach

The governing equations are derived for the particle model, and then converted into non‐dimensional form using reference quantities. The non‐dimensional equations are discretised on a uniform spherical grid fitted to the particle using finite difference method. The resulting algebraic equations are solved using Tri‐Diagonal Matrix Algorithm, and the governing equations are derived for the bed model, and then converted into non‐dimensional form using reference quantities. The non‐dimensional equations are discretised explicitly on a one‐dimensional and uniform grid fitted to the bed. The unknown quantities are evaluated using the corresponding values at the previous time interval.

Findings

The results obtained from numerical modeling show that, when the particle has a low diffusion resistance or a high chemical resistance, the reaction takes place slowly and homogeneously throughout the ore particle. On the other hand, when the bed has a low convection resistance, the reaction takes place homogeneously throughout the bed. As the convection resistance increases, the non‐homogeneous (local) behavior predominates. It is also noticed that, when the chemical reaction resistance is high, the reaction takes place homogeneously throughout the bed.

Research limitations/implications

The dynamic diffusion and movement of solution in the ore particles and ore bed are not modeled and volumetric ratio of solution in the particles and the bed and also vertical velocity of solution in the bed are assumed to be fixed constants.

Practical implications

This study shows that the reaction takes place homogeneously throughout the bed when the convection resistance is low, the diffusion resistance is high, the concentration resistance is low, and the chemical reaction resistance is high.

Originality/value

Homogeneous reaction conditions being suitable for heap leaching operations are identified. Thus, it is recommended to approach the above conditions when preparing ore heaps and designing the relevant operation.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 17 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 3 June 2019

Soufyane Bellifa and Nadir Boumechra

This paper aims to assess the effects of chemically accelerated leaching on the physical and mechanical properties of aerial lime–cement mortars (LCMs).

Abstract

Purpose

This paper aims to assess the effects of chemically accelerated leaching on the physical and mechanical properties of aerial lime–cement mortars (LCMs).

Design/methodology/approach

Two aerial LCMs, differencing mainly in their calcium hydroxide content, were degraded by the use of an ammonium nitrate solution as a leaching agent. The leaching effects were studied by evaluating the rate of change in physical (sorptivity and mass loss) and mechanical (flexural and compressive strength) characteristics of aerial LCMs. To quantify the evolution and kinetics of degradation, the leached depth was then characterized at different levels of degradation by means of a phenolphthalein solution.

Findings

The experimental results showed that the dissolution of binder decreases the mass, alkalinity and strength of aerial LCMs but increases their sorptivity. A linear relationship was derived by plotting the values of leached depth against the square root of immersion time in an aggressive solution. It was found that the leached depth followed diffusion-controlled kinetics.

Originality/value

It was found that the global loss of compressive strength of aerial LCMs because of complete dissolution of calcium hydroxide can reach up to 80 per cent.

Details

Journal of Engineering, Design and Technology , vol. 17 no. 3
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 1 February 1986

W. Leibfried

This paper outlines methods and results of wetting, leaching and adhesion analyses on copper thick film conductors over alumina and multilayer glasses after different…

Abstract

This paper outlines methods and results of wetting, leaching and adhesion analyses on copper thick film conductors over alumina and multilayer glasses after different processing conditions. The intention is to provide a better background for evaluating and optimising materials and processing conditions in copper thick films and working out quick, reliable and quantitative methods for better characterisation of copper conductors in production. For these reasons the following methods were used: (a) wetting and leaching analyses with a scanning wetting balance, working in nitrogen, (b) pull tests with solder contacts on copper thick film conductors after soldering, ageing and thermal cycling, and (c) some additional surface analyses (REM, EDX, Auger) for a better understanding of copper pastes and their material interactions, when processed under different conditions. The results are summarised under three general aspects: surface structure and wetting of copper thick films, wetting and leaching of various copper thick films after different processing conditions, and finally the influence of different wetting properties of such surfaces on the solder adhesion strength after soldering, ageing and thermal cycling. The results give good insight into the various interactions of copper thick films with their substrate materials and confirm the ability of the described wetting and leaching analyses for these purposes.

Details

Microelectronics International, vol. 3 no. 2
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 14 November 2016

Jiang Hu

The multi-scale numerical simulation method, able to represent the complexity of the random structures and capture phase degradation, is an effective way to investigate…

Abstract

Purpose

The multi-scale numerical simulation method, able to represent the complexity of the random structures and capture phase degradation, is an effective way to investigate the long-term behavior of concrete in service and bridges the gap between research on the material and on the structural level. However, the combined chemical-physical deterioration mechanisms of concrete remain a challenging task. The purpose of this paper is to investigate the degradation mechanism of concrete at the waterline in cold regions induced by combined calcium leaching and frost damage.

Design/methodology/approach

With the help of the NIST’s three-dimensional (3D) hydration model and the random aggregate model, realistic 3D representative volume elements (RVEs) of concrete at the micro-, the meso-, and the macro-scales can be reconstructed. The boundary problem method is introduced to compute the homogenized mechanical properties for both sound and damaged RVEs. According to the damage characteristics, the staggering method including a random dissolution model and a thermo-mechanical coupling model is developed to simulate the synergy deterioration effects of interacted calcium leaching and frost attacks. The coupled damage procedure for the frost damage process is based on the hydraulic pressure theory and the ice lens growth theory considering the relationship between the frozen temperature and the radius of the capillary pore. Finally, regarding calcium leaching as the leading role in actual engineering, the numerical methodology for combined leaching and frost damage on concrete property is proposed using a successive multi-scale method.

Findings

On the basis of available experimental data, this methodology is employed to explore the deterioration process. The results agree with the experimental ones to some extent, chemical leaching leads to the nucleation of some micro-cracks (i.e. damage), and consequently, to the decrease of the frost resistance.

Originality/value

It is demonstrated that the multi-scale numerical methodology can capture potential aging and deterioration evolution processes, and can give an insight into the macroscopic property degradation of concrete under long-term aggressive conditions.

Details

Multidiscipline Modeling in Materials and Structures, vol. 12 no. 4
Type: Research Article
ISSN: 1573-6105

Keywords

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Article
Publication date: 1 November 1967

D. Tuitt

SEVERE natural exposure and laboratory test, dry salt/humidity, have both shown the advantages of primers that leach chromate over similar primers that do not. This…

Abstract

SEVERE natural exposure and laboratory test, dry salt/humidity, have both shown the advantages of primers that leach chromate over similar primers that do not. This advantage, applicable to both primer only and primer plus finish schemes, is paticularly evident where there are breaks, in the paint film due to edges, damage or paint cracking round rivet heads Several other laboratories have used other tests and have reached the same general conclusions. Sufficient experimental work has been carried out to formulate primers with very different leach rate characteristics. Many of these have been produced and are now being corrosion tested When the results are available it is hoped that they will be sufficiently consistent to enable a leaching test to be included in some paint specifications instead of the present two year corrosion test. Until then it is suggested that this fairly simple test provides a useful means of screening new primers for the paint industry and, for the aircraft constructor, one possible way of chuosing between the several competitive schemes offered to him, without having to wait many years for the results of corrosion lasts.

Details

Aircraft Engineering and Aerospace Technology, vol. 39 no. 11
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 26 July 2013

Lena Hallin‐Pihlatie, Jaana Rintala and Henning Sten Hansen

The objective of this paper is to describe an easily understandable integrated modelling framework for analysing the combined effects of changes in land‐use and climate on…

Abstract

Purpose

The objective of this paper is to describe an easily understandable integrated modelling framework for analysing the combined effects of changes in land‐use and climate on the leaching of phosphorus using regional IPCC‐based land‐use and climate scenarios. In addition, the paper reflects on the added value of a geospatial data‐based modelling approach from a river basin management perspective.

Design/methodology/approach

Regional land‐use scenarios were simulated for the whole official river basin planning unit of the Oulujoki‐Iijoki River Basin District using a land‐use simulation model. The nutrient leaching modelling on phosphorus was carried out in another raster‐based freeware for a smaller sub‐basin, Temmesjoki river basin.

Findings

Regional land use scenarios could be simulated taking into account the local conditions, such as the vicinity to water, and development options in agriculture on regional scale. The magnitude and leaching pattern of phosphorus in the future is related to the overall share of agricultural land on drainage basin level. The authors’ results also indicate that the local spatial structure of built‐up and agricultural areas may play a central role in nutrient leaching assessment. If the spatial structure is of importance, this may have further implications for the environmental planners working with river basin management.

Originality/value

This research takes a step further in bringing the global scenario framework to the local and practical level for various practical purposes in river basin management. The research provides an approach to spatially identify the possible impact of changes in land‐use and in climatic conditions on nutrient leaching.

Details

International Journal of Climate Change Strategies and Management, vol. 5 no. 3
Type: Research Article
ISSN: 1756-8692

Keywords

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Article
Publication date: 26 September 2009

Koen Mondelaers, Joris Aertsens and Guido Van Huylenbroeck

This paper aims to perform a meta‐analysis of the literature comparing the environmental impacts of organic and conventional farming and linking these to differences in…

Abstract

Purpose

This paper aims to perform a meta‐analysis of the literature comparing the environmental impacts of organic and conventional farming and linking these to differences in management practises. The studied environmental impacts are related to land use efficiency, organic matter content in the soil, nitrate and phosphate leaching to the water system, greenhouse gas emissions and biodiversity.

Design/methodology/approach

The theoretic framework uses the driver‐state‐response framework and literature data were analysed using meta‐analysis methodology. Meta‐analysis is the statistical analysis of multiple study results. Data were obtained by screening peer reviewed literature.

Findings

From the paper's meta‐analysis it can conclude that soils in organic farming systems have on average a higher content of organic matter. It can also conclude that organic farming contributes positively to agro‐biodiversity (breeds used by the farmers) and natural biodiversity (wild life). Concerning the impact of the organic farming system on nitrate and phosphorous leaching and greenhouse gas emissions the result of the analysis is not that straightforward. When expressed per production area organic farming scores better than conventional farming for these items. However, given the lower land use efficiency of organic farming in developed countries, this positive effect expressed per unit product is less pronounced or not present at all.

Original value

Given the recent growth of organic farming and the general perception that organic farming is more environment friendly than its conventional counterpart, it is interesting to explore whether it meets the alleged benefits. By combining several studies in one analysis, the technique of meta‐analysis is powerful and may allow the generation of more nuanced findings and the generalisation of those findings.

Details

British Food Journal, vol. 111 no. 10
Type: Research Article
ISSN: 0007-070X

Keywords

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Book part
Publication date: 18 July 2007

Thomas G. Schmidt

This chapter describes a method to analyse agricultural land use in terms of net value added and employment (working time requirement) in the agricultural sector as well…

Abstract

This chapter describes a method to analyse agricultural land use in terms of net value added and employment (working time requirement) in the agricultural sector as well as a corresponding ecological indicator: the nitrogen-leaching-rate. Watershed management demands a basic approach, which deals with common statistics and spatial information from digital maps. This causes a range of uncertainties, which are calculated in relation to the data input. A metamodel derived from a process model calculates the most probable value of the ecological indicator, whereas the economic indicators are estimated by the cumulative numbers of primary production. The uncertainties are expressed as the standard deviation of all impacts as percentages. The method described is applied to a rural district in the Elbe river basin.

Details

Ecological Economics of Sustainable Watershed Management
Type: Book
ISBN: 978-1-84950-507-9

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Article
Publication date: 1 October 2004

Stig Lande, Mats Westin and Marc H. Schneider

This paper aims to show the potential decay resistance of furfurylated wood and investigate possible eco‐toxicity of such materials produced. This paper deals with the…

Abstract

This paper aims to show the potential decay resistance of furfurylated wood and investigate possible eco‐toxicity of such materials produced. This paper deals with the environmental aspects and durability of furfurylated wood, both laboratory and field tests are included in the investigations. Results from several decay tests, emission analysis studies and ecotox tests are presented. The results show that furfurylated wood is highly decay resistant. Furthermore, no significant increase in eco‐toxicity of leaching water was found and degradation through combustion does not release any volatile organic compounds or poly‐aromatic hydrocarbons above normal levels for wood combustion. Durability enhancement by furfurylation of wood is not believed to be harmful to the environment. Wood modified with furfuryl alcohol, “furfurylated wood”, is currently being marketed as a non‐toxic alternative to traditional preservative treated wood (wood impregnated with biocides). This paper summarises much of the long term exposure of furfurylated wood ever caried out, and present the first eco‐tox tests on such material ever done.

Details

Management of Environmental Quality: An International Journal, vol. 15 no. 5
Type: Research Article
ISSN: 1477-7835

Keywords

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Article
Publication date: 1 February 1990

M.M.H. Ayoub, M.M. Abdel Malek and N.N. Messiha

An organotin copolymer with tin content of 22% was prepared by the reaction of methyl methacrylate and tri‐n‐butyltin methacrylate. The prepared copolymer was incorporated…

Abstract

An organotin copolymer with tin content of 22% was prepared by the reaction of methyl methacrylate and tri‐n‐butyltin methacrylate. The prepared copolymer was incorporated into a paint formulation containing cuprous oxide as an external toxin. Laboratory evaluation of the formulation showed that the average value of the leaching rate of Cu was 7 µg/cm2/day, while the leaching rate of tin was found to be in the range of 0.033 µg/cm2/day. The antifouling performance of the prepared formulation was tested as painted areas on the hull of a trading ship. After about one year's running period through the Mediterranean and Red Sea harbours the tested areas showed good antifouling efficiency compared with the commercial antifouling paint.

Details

Pigment & Resin Technology, vol. 19 no. 2
Type: Research Article
ISSN: 0369-9420

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