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The aim of this study is to discuss the importance of characterization of green, waste green and reclaimed sand. The transformations and changes which take place in the green sand, are due to the casting process. Green sand which loses its properties during the casting process at a high temperature of molten metal results into waste green sand. Various techniques are applied for characterization of foundry sands. They include Universal Testing machine (UTM) for compressive and shear strengths, texture analyzer for impact test, Thermogravimetric Analysis (TGA) for weight loss kinetics, Inductively Coupled Plasma (ICP-AES) for elemental composition, sieves for Grain Fineness Number (GFN), permeability tester for permeability number of the mold, X-Ray Diffraction (XRD) for crystallinity, Scanning Electron Microscopy (SEM) for morphology and Fourier Transform Infrared spectroscopy (FTIR) for organic functional groups. The waste green sand after being reclaimed in two- stage attrition device, through mechanical attrition, has been later compared with the fresh sand. This study confirms that reclaimed sand can be used either directly for molding or it can be mixed with the appropriate amount of fresh sand.

Green sand molds in foundry use bentonite as a binder. During the casting process, the heat transferred to the surrounding sand in the mold leads to the degradation of bentonite structure, thereby forming new types of deposits on the surface of sand grain. This results in deactivation of binder and unsuitability of sand for its reuse. In the present work, useful insights are provided into this transformation that may help in developing technology to reclaim the sand for its reuse in foundry. The green sand and bentonite were subjected to high temperatures over the range 500 °C–1100 °C, for varying periods (10–120 min) and analyzed. It was found that the binder in the used sand existed in four different forms. These were active clay, loosely bound dead clay, strongly bound sintered clay and high-temperature phases; the latter three forms need to be removed in the reclamation process. While a simple mechanical attrition method can remove the loosely bound dead clay, it fails in removing the other two forms, that are referred as oolitic deposits of sintered clay and high-temperature phases. More aggressive attrition or chemical treatment may be necessary to facilitate their removal. Analytical methods such as FTIR, DSC, SEM, and X-ray diffraction were used to show the differences between clay binder and oolitic deposits and how the transformation takes place from one form to the other as a function of temperature. Furthermore, the kinetics of oolitic formation was examined and the results showed that the formation of oolitic deposits follows temperature-dependent first-order kinetics.

This article presents a holistic approach to promote waste foundry sand (WFS) reclamation in India by designing a framework for a multistakeholder approach that combines resources, technology, and potential market. The scale of WFS generation and dumping is estimated based on a survey, and a solution is proposed that integrates WFS collection and sand reclamation technology for foundry sand ecosystem development. The study further examined the economic feasibility of a mechanical reclamation process for WFS, using indicators such as net present value (NPV), internal rate of return (IRR), discounted payback period (DPBP), and benefit-cost ratio (BCR). A sand reclamation plant of 1 ton h−1 capacity showed promising economics, and the NPV, IRR, DPBP, and BCR were found to be ₹57.21 million ($0.76 million), 29.78%, 2.82 years, and 5.48, respectively. All the operating, manpower, raw material, and utility costs reasonably influence the economics of the reclamation process. In parallel, sensitivity and uncertainty analyses were carried out using a Monte Carlo simulation to understand the influence of the above-mentioned indicators on the economics of the process. This uncertainty analysis predicted an average NPV of ₹56.55 ± 2 million ($0.75 ± 0.027 million). The castings made up of reclaimed sand appeared to be cost competitive at the reclaimed sand price in the range of ₹1000–2000 ton−1 ($13.33–26.67 ton−1). Overall, the designed framework appears to encourage reduction in WFS disposal and promotion of reclaimed sand in Indian foundries. Policy interventions are suggested to promote the proposed solution in its initial phase.

Binder material (e.g. bentonite, polymeric resins) is used for producing molds and cores in foundries. It deactivates upon exposure to the high temperature (~1400°C) of molten metal. As a result, these binders form either loosely or strongly bound deposits on the surface of sand grains, leaving them unsuitable for further use. Disposal of Waste Foundry Sand (WFS) remains to be one of the significant challenges faced by foundry industry nowadays. In order to remove these deposits from WFS, we have studied and compared two types of methods namely, mechanical and thermal reclamation. The WFS samples after being reclaimed either mechanically or thermally or by combination of both, are compared using various tests. These tests include determination of loosely bound and strongly bound clay content, compressive strength, Grain Fineness Number (GFN), Loss on Ignition (LOI), Acid Demand Value (ADV), Particle size distribution and optical microscopy. We have used the aforementioned tests to characterize the quality of foundry sand and the suitability of reclaimed sand for use in mold and core production in foundries. The results showed that neither of these treatments is sufficient to completely remove the deposits from sand grains. However, solely mechanically reclaimed sand is suitable for the mold production after maintaining 8% active clay and 10% loosely bound clay in the reclaimed sand, respectively.

Disposal of Used Foundry Green Sand (UFGS) remains one of the significant challenges faced by foundry industry nowadays. Experiments were performed to reduce the total clay content from 12% to as low as 2.2% in waste foundry sand. Three prototypes were developed during the course of this work. They include vertical fluidized bed, horizontal fluidized bed and a novel ball-mill type attrition and sieving unit. The cost per ton of reclaimed sand is higher in case of fluidized bed based prototypes while in case of attrition and sieving based prototype, it is less than half of the cost of the fresh sand. The experimental data generated on the two-stage attrition and sieving unit under different conditions is further used to arrive at a semi-empirical correlation and the optimum set of design and operating parameters to get the best performance.

The bauxites deposits of Kachchh area in Gujarat are investigated to characterize them based on mineralogical and petrographic studies. The major bauxitic mineral in these occurrences is gibbsite, with minor concentration of boehmite and diaspore. Apart from the bauxitic minerals, the other associate minerals are kaolin, calcite, alunite and the iron ore minerals such as hematite and goethite and titanium rich anatase. The iron ore minerals (hematite and goethite) are 10-50microns in size and are disseminated throughout the oolitic and pisolitic bauxitic minerals. At places the goethite exhibits colloform texture. The preservation of basaltic texture in some of the samples indicate that the insitu nature of these bauxites, which are formed by the alteration of calcic plagioclase from the parent basalt. Although, the basalt occurs as the main parent rock for these bauxites, the presence of calcite in some of the samples represent the possibility of having a limestone parent rock at least in some of the bauxite occurrences.

Characterization of fluid inclusions in graphite-bearing charnockites from the southwestern part of the Madurai Granulite Block in southern India reveals a probable relation with the formation and break down of graphite during the high-grade metamorphism. The first-generation monophase pure CO(2) inclusions, the composition of which is confirmed by laser Raman spectroscopy, recorded moderate density (0.77-0.87 g/cc) corresponding to low tapping pressure (around 2 kb) than that of the peak granulite-facies metamorphism. The precipitation of graphite, as inferred from graphite inclusions and delta(13)C values of the graphite from the outcrops, is interpreted as the cause of this lowering of fluid density. An intermediate generation of pseudosecondary inclusions resulted from the re-equilibration or modification of the first-generation fluids and the CO(2). formed is interpreted to be the oxidation product from graphite. The youngest generation of fluids which caused widespread retrogression of the granulites is a low-temperature (similar to 350 degrees C) high-saline (32.4-52.0 wt% NaCl equivalent) brine. Carbon isotope data on the graphite from the charnockites show delta(13)C values ranging from -11.3 to -19.9 parts per thousand, suggesting a possibility of mixing of carbon sources, relating to earlier biogenic and later CO(2) fluid influx. Combining the information gathered from petrologic, fluid inclusion and carbon stable isotope data, we model the fluid evolution in the massive charnockites of the southwestern Madurai Granulite Block. (c) 2009

The discussion on our paper (Pandalai et al. 2003) by Kolb et al. (2003, DOI 10.1007/s00126-002-0345-9) raises important issues related to the genesis of the Hutti gold deposit. The main points raised by Kolb et al. (2003) relate to the estimation of P and T of ore formation and the chronological (and genetic) order of vein formation in the shear zones at Hutti as identified by them. Rogers et al. (2002) and Kolb et al. (2003) recognize five stages of deformation (D1–D5), one prograde (M1) and two retrograde (M2, M3) stages of metamorphism, and four stages of quartz vein formation with attendant alteration. Rogers et al. (2002) and Kolb et al. (2001, 2003) do not refer to previously published literature on structural studies of the Hutti–Maski schist belt. Nevertheless, the deformational stages identified by Kolb et al. (2003) need to be placed in the framework of the regional tectonic history of the Hutti–Maski belt. Structural studies on this belt are reported in Roy (1979, 1991) and Biswas (1990). These studies identify three phases of deformation and metamorphism that are codified here as D1 , D2 , D3 * and M1 , M2 * , M3 * respectively to distinguish them from those of Kolb et al. (2003). A brief summary of the structural framework is given below before discussing the points raised in Kolb et al. (2003). The first deformational stage (D1 ) led to the development of tight isoclinal (F1 ) folds, penetrative schistosity (S1 ), synchronous prograde metamorphism (M1 ) and syntectonic emplacement of tonalite and tronjhemite around the Hutti–Maski belt. Additionally, mylonite and mylonitic foliation (Sm ) developed in narrow shear zones. On account of the parallelism of Sm * with S1 * it is inferred that they developed during the phase of D1 * deformation. The prograde M1 * phase of metamorphism is low grade (greenschist facies), but rises to medium grade (amphibolite facies) with development of garnet and cordierite in the north-eastern peripheral zone of the greenstone belt. The D2 * deformation stage gave rise to small and large-scale (F2 ) folds with subvertical axial planes (S2 ) and axes that plunge 50 to 60 NW. F2 folds bring F1 isoclinal folds into parallelism with F2 * limbs and are responsible for the map pattern of the exposed rocks. S2 *

The pressure, temperature and composition of ore fluids that resulted in gold deposition in the Archean, greenstone-hosted Hutti deposit have been studied using fluid inclusions and the compositions of arsenopyrite and chlorite. Five types of fluids have been identified in fluid inclusions in quartz veins associated with mineralization. They are (1) monophase CO2-rich fluid; (2) low-salinity (0 to 14 wt% NaCl equivalent) and high-salinity (16 to 23 wt% NaCl equiv.) aqueous fluids; (3) high-salinity (28 to 40 wt% NaCl equiv.), polyphase aqueous fluids; (4) CO2-H2O-NaCl fluids of low salinity (0-8 wt% NaCl equiv.); and (5) a few carbonic inclusions with halite +/-nahcolite. The diversity of entrapped fluid composition is explained in terms of changes in fluid pressure and temperature which affect a more or less uniform supply of primary low-salinity CO2-H2O-NaCl fluid to the shear zone. Geothermobarometric studies indicate that during mineralization temperature ranged between 360 and 240degreesC, and fluid pressure between 3,600 and 1,600 bar. The data are interpreted in terms of the cyclic fault-valve mechanism for active shear zones. Deposition of gold and sulfides has been studied on the basis of constraints from the composition of wall-rock chlorite, ore-mineral assemblages, and textural features. Tubular channels, 20 to 100 pm wide and up to 500 mum long that arise from fractures and C-planes in sheared quartz veins are reported for the first time. The channels have pyrrhotite, arsenopyrite, pyrite and gold at their distal ends, with calcite filling up the remaining part. These channels form in response to increases in T and P, by dissolution of quartz grains, guided by dislocations in them. At the P-T conditions of interest, gold and sulfide deposition takes place in the shears and fractures of quartz veins from CO2-H2O-NaCl ore fluid of low salinity and pH due to changes in phase compositions that occur during the process of shear failure of the enclosing rocks. In the wall rock where pH is buffered, gold deposition takes place from the predominant Au(HS)(2)(-) species with progressive sulfide deposition and decrease in YES, from 0.01 to 0.001 mol/kg as T falls from 360 to 240degreesC.

The Proterozoic, carbonate-hosted, Zawarmala Pb-Zn deposit has stratiform, banded pyrite-sphalerite ore, as well as discordant, sphalerite-galena veins and rich massive galena ore shoots. The mechanisms of deposition of discordant vein and massive ores have been studied using speciation and solubility calculations based on ore fluid characteristics and physical parameters inferred from petrography, fluid inclusion studies, and leachate analysis. Massive galena ore, which is the economic ore type, cuts across the earlier, F2-related, vein-type ore and is distinct from the vein-type ore in terms of mineralogy, texture, and fluid inclusion characteristics. Fluid inclusions in quartz associated with the ores show that fluids forming vein-type ore are low-salinity (4.3–14.7 wt % NaCl equiv) H2O-NaCl fluids. The trapping temperature of vein-type ore fluid was estimated to be in the range of 395° to 290°C at a pressure of about 1,450 bars. Fluids associated with massive galena ore are H2O-CO2-NaCl fluids of lower salinity (about 3–4 wt % NaCl equiv). The wide variation in XCO2 of fluid inclusions that occur in close proximity to each other within the same sample of massive ore suggests heterogeneous entrapment of the low-salinity H2O-CO2-NaCl fluids. From the intersection of isochores of local, homogeneously entrapped CO2 and aqueous biphase fluids of unmixed CO2-H2O-NaCl fluid, trapping temperature fluid was estimated to be between 250° and 150°C at pressures of 2,000 to 750 bars. Despite the low salinity of the ore fluids, speciation studies show that chloride complexes are dominant over most of the temperature range of interest in both ore fluids. The only bisulfide complex of importance is \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(Pb(HS)_{2}^{0}\) \end{document}, which is dominant below 175°C in fluids associated with massive galena ore. Data from fluid inclusions and solubility calculations reveal that cooling is the important mechanism of vein-type ore deposition. In contrast, physicochemical data indicate that an increase in reduced sulfur, by mixing a regional, high metal content, low sulfur fluid with a local, high sulfur fluid at the site of deposition, was the mechanism for massive galena ore deposition. The difference in oxidation state (and therefore also in metal content) of the two fluids is inferred to be a significant factor that caused differences in the modes of deposition of the two ore types and the relatively high value of XCO2 (0.2033) in fluids associated with massive galena ore.

Fluid inclusions and melt inclusions have been considered as possible guides for mineral exploration by many researchers. However, the minuteness of the fluid inclusions and the multiplicity of generations within the same deposit have always posed serious problems in the proper utilization of fluid-inclusion data in prospecting.

The migration of heat in porous media has attracted attention of the research fraternity, since almost a century. Studies conducted in the past reveal that heat migration in a medium primarily depends on its thermal resistivity (defined as the ability of the material to resist heat flow in it), its specific heat (defined as the ability of the material to store heat) and thermal diffusivity (which combines the transmission and storage properties of the material and is an indicative of the rate of change of temperature within the material)., © Elsvier