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Rendon-Angeles J.C.,National Polytechnic Institute of Mexico | Rendon-Angeles J.C.,Research Institute of Advanced Studies | Matamoros-Veloza Z.,Technological Institute of Saltillo | Lopez-Cuevas J.,National Polytechnic Institute of Mexico | And 3 more authors.
International Journal of Mineral Processing | Year: 2016

The conversion reaction of three feedstock particle sizes (< 38-165 μm) of celestine (SrSO4) powders into SrWO4 particles with scheelite structure was investigated in highly concentrated NaOH solutions saturated with the chemical reagent Na2WO4. The hydrothermal treatments were carried out over the range of 150-225 °C for several reaction intervals (1-6 h). The complete conversion of SrSO4 into SrWO4 under non-stirred conditions was found to proceed rapidly on fine SrSO4 particles (< 38 μm) by increasing the concentration of the alkaline fluid, and the conversion to SrWO4 was completed at 200 °C for 6 h in a 5 M NaOH solution. The crystallization of the SrWO4 particles occurred rapidly by stirring the autoclave at a speed of 20 rpm, even when larger SrSO4 particles (165 μm) were hydrothermally converted at a low temperature of 150 °C for 4 h. The conversion was further accelerated by increasing the reaction temperature and employing small feedstock particle sizes, < 38 and 69 μm. The SrWO4 particles morphology resembled a quasi-octahedral shaped and consisted of fine particles with bimodal sizes between 0.9 and 2.5 μm. A typical tendency toward particle agglomeration was observed during the crystallization of the SrWO4 particles, which after the longest reaction intervals produced agglomerates with a size of 50 μm. Bulk dissolution of the mineral SrSO4 powder coupled with a massive precipitation produced the formation of SrWO4 particles. A kinetic analysis was carried out for the conversion of large SrSO4 particles (165 μm) into SrWO4 using the diffusion controlled kinetic model proposed by Jander. The activation energy determined for the global conversion process of the quasi-octahedral shaped SrWO4 particles was 18.30 kJ mol- 1. © 2016 Elsevier B.V. All rights reserved. Source

Resendiz-Flores E.O.,Technological Institute of Saltillo | Garcia-Calvillo I.D.,Autonomous University of Coahuila
International Journal of Heat and Mass Transfer | Year: 2015

This paper presents the application of the Finite Pointset Method for the numerical solution of three dimensional and non-stationary heat conduction problems. The strong formulation of the parabolic partial differential equation is directly used instead of the corresponding weak form. Moreover, a numerical comparison between the Finite Pointset Method and the corresponding analytical solutions is reported. © 2015 Elsevier Ltd. All rights reserved. Source

Moncayo-Martinez L.A.,Technological Institute of Saltillo | Zhang D.Z.,University of Exeter | Zhang D.Z.,Chongqing University
International Journal of Production Economics | Year: 2013

The problem of placing safety inventory over a network, which assembles a product, is a challenging issue in supply chain design (SCD) because manufacturers always want to reduce inventory all over the supply chain (SC). Moreover, the process of designing a SC and then placing inventory, to offer high service level at the lowest possible cost, across a complex SC, is not an easy task for decision makers. In this paper we use the SC representation proposed by Graves and Willems (2000), Manufacturing & Service Operations Management 2 (1), 68-83, where a SC is divided into many supplying, manufacturing, and delivering stages. Our problem is to select one resource option to perform each stage, and based on the selected options to place an amount of inventory (in-progress and on-hand) at each stage, in order to offer a satisfactory customer service level with as low as possible total supply chain cost. A resource option here represents a supplier, a manufacturing plant (production line), or a transport mode in a supplying, manufacturing, or delivering stage, respectively. We developed an approach based on ant colony optimisation (ACO) to minimise simultaneously the total supply chain cost and the products' lead time to ensure product deliveries without delays. What are new in our approach are the bi-objective function and the computational efficiency of our ACO-based approach. In addition, ACO has not been applied to solve the inventory placement problem. As a validation of the model, we: (a) describe a successful application at CIFUNSA, one of the largest iron foundry in the world, and (b) compare different CPU time instances and metrics about multi-objective optimisation. © 2013 Elsevier B.V. Source

Luna A J.S.,CINVESTAV | Flores V A.,CINVESTAV | Muniz V R.,Autonomous University of Coahuila | Fuentes A.F.,CINVESTAV | And 4 more authors.
Journal of Rare Earths | Year: 2011

This work presented the feasibility of cerium recovery by Al-Mg alloy through the metallothermic reduction of CeO2 to obtain a master alloy Al-4Ce. The master alloy obtained in this investigation was for the grain refinement and modification of Al-Si alloys. The reagent was incorporated into a molten alloy using the submerged powder injection technique, and metallic samples were obtained during injection. Chemical and microstructural analyses (by inductively coupled plasma (ICP) and scanning electron microscopy (SEM), respectively) confirmed the possibility of Ce uptake in the bath (0 to 4 wt.), as CeO2 was reduced through metallothermic reactions in the molten alloys. Based on the characterization of reaction products, the sequence of the reaction was proposed. © 2011 The Chinese Society of Rare Earths. Source

Matamoros-Veloza Z.,Technological Institute of Saltillo | Rendon-Angeles J.C.,Research Institute for Advanced Studies of the NPI | Rendon-Angeles J.C.,Research Institute for Advanced Studies of the NPI | Yanagisawa K.,Kochi University | And 2 more authors.
Ceramics International | Year: 2015

The influence of aqueous solutions (deionized water or Na2CO3 solutions, 0.1-0.5 M) and other processing parameters such as temperature (150-250 °C) for preparing hydrothermal hot-pressed TV panel waste glass compacts was investigated to produce porous glass specimens. Waste powdered glass (5 g) from old analog Philips television panels (Mexico) with particle sizes of <38 μm was mixed with various amounts of the selected aqueous solution (5-20 wt%). The TV glass panel particles dissolved in all of the mineralizer solution that were employed, and the behavior was controlled by the amount of aqueous solution added to the glass powder densification stage. The reactions of the glass particles with water or Na2CO3 solutions produced a solid glass phase that included water molecules or Na+ and CO3-2 ions, respectively. The hydrothermal hot press (HHP)-treated glass compacts prepared at 200 °C for 2 h at a constant loading pressure of 20 MPa exhibited a marked expansion after heat treatment conducted at 700 °C for 1 h in an air atmosphere. The expansion of the HHP compacted TV panel glass specimens was further increased for the samples prepared with 0.5 M Na2CO3 solution; these foamed glasses exhibited the lowest apparent densities that varied from 0.309 to 0.319 g/cm3. © 2015 Elsevier Ltd and Techna Group S.r.l. Source

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