Quantification Of Pyrrhotiye O2 Consumption By Using Pyrite Oxidation Kinetic Data

2014 ◽  
Vol 1665 ◽  
pp. 93-101
Author(s):  
I. Rojo ◽  
F. Clarens ◽  
J. de Pablo ◽  
C Domènech ◽  
L. Duro ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pyrite Oxidation ◽  
Oxidation Kinetic ◽  
Dissolution Kinetics ◽  
Buffering Capacity ◽  
Uptake Capacity ◽  
Kinetic Rate ◽  
Oxidation Rates ◽  
Redox Pair ◽  
Kinetics Of

ABSTRACTExperiments on the dissolution kinetics of natural pyrrhotite (FeS1-x-) and pyrite (FeS2) under imposed redox conditions to evaluate the oxygen uptake capacity of both minerals were carried out at 25°C and 1 bar. Experimental data indicate that in both cases, Fe(II) released from dissolution of these Fe-bearing sulphides is kinetically oxidized to Fe(III) to precipitate as Fe(III)-oxyhydroxides. While the system is pH controlled by the extent of the sulphide oxidation, Eh is controlled by the redox pair Fe2+/Fe(III)-oxyhydroxides. Pyrrhotite dissolution is faster than that of pyrite but generates less acidity. Consequently, the achieved redox value is more reducing. Experimental data show that the oxidation rates of both minerals (in mol·g-1·s-1) are equivalent under the studied conditions. This fact gives a new opportunity to quantify the reductive buffering capacity of pyrrhotite, for which no kinetic rate law has been still established.

scholarly journals Dissolution of Tunisian phosphate ore by a mixture of sulfuric and phosphoric acid: Kinetics study by means of differential reaction calorimetry

2019 ◽  
Vol 55 (1) ◽  
pp. 9-19
Author(s):  
Olfa Lachkar-Zamouri ◽  
Khemaies Brahim ◽  
Faten Bennour ◽  
Ismail Khattech
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Dissolution Rate ◽  
Dissolution Kinetics ◽  
Reaction Model ◽  
Reaction Calorimetry ◽  
Phosphate Ore ◽  
Differential Reaction ◽  
Apparent Activation Energies ◽  
Kinetics Of

A mixture of phosphoric and sulfuric acid was used to investigate the dissolution kinetics of phosphate ore by Differential Reaction Calorimetry (DRC). The effect of the solid-to-iquid ratio, concentration, stirring speed, particle size and temperature of the reaction is examined. It was established that the dissolution rate increased with stirring speed and particle size. However, rising the olid-to-iquid ratio, temperature and concentration decreased the dissolution rate. It was determined that the dissolution rate fits in the first order of the pseudo-homogeneous reaction model. Two negative values of apparent activation energies were found in the range of 25 to 60?C. The experimental data were tested by graphical and statistical methods and it was found that the following models were best fitted for the experimental data and an empirical equation for the process was developed. -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (2671/T)]t. T? 40?C -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (6959/T)]t. T > 45?C

scholarly journals The Influence of Woven Fabric Structure on Kinetics of Water Sorption

2014 ◽  
Vol 9 (1) ◽  
pp. 155892501400900
Author(s):  
Mohamed Hamdaoui ◽  
Nesma Sawssen Achour ◽  
Sassi Ben Nasrallah
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Water Sorption ◽  
Cotton Fabrics ◽  
Woven Fabric ◽  
Model Parameters ◽  
Kinetic Rate ◽  
Weave Structure ◽  
Fabric Structure ◽  
Kinetics Of

In this paper, the results of an experimental study designed to determine the kinetics of water sorption on cotton fabrics are presented. The dynamic water sorption of cotton fabrics was gravimetrically investigated at 20°C by using an experimental device, which assured the vertical suspension of the cloth surface and permitted the measurement of the mass of liquid rising in the fabric. A good fit of the experimental data with the parallel exponential kinetics model was found. The results show that the weave structure and the number of yarns per centimeter had a significant influence on the model parameters and the kinetic rate of sorption.

scholarly journals Dissolution of the Primary γ′ Precipitates and Grain Growth during Solution Treatment of Three Nickel Base Superalloys

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1921
Author(s):  
Karen Alvarado ◽  
Ilusca Janeiro ◽  
Sebastian Florez ◽  
Baptiste Flipon ◽  
Jean-Michel Franchet ◽  
...  
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Solution Treatment ◽  
Dissolution Kinetics ◽  
Second Phase ◽  
Stable States ◽  
Size Evolution ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Kinetics Of

Second phase particles (SPP) play an essential role in controlling grain size and properties of polycrystalline nickel base superalloys. The understanding of the behavior of these precipitates is of prime importance in predicting microstructure evolutions. The dissolution kinetics of the primary γ′ precipitates during subsolvus solution treatments were investigated for three nickel base superalloys (René 65, AD730 and N19). A temperature-time codependency equation was established to describe the evolution of primary γ′ precipitates of each material using experimental data, the Thermo-Calc software and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. The dissolution kinetics of precipitates was also simulated using the level-set (LS) method and the former phenomenological model. The precipitates are represented using an additional LS function and a numerical treatment around grain boundaries in the vicinity of the precipitates is applied to reproduce their pinning pressure correctly. Thus, considering the actual precipitate dissolution, these simulations aim to predict grain size evolution in the transient and stable states. Furthermore, it is illustrated how a population of Prior Particle Boundaries (PPB) particles can be considered in the numerical framework in order to reproduce the grain size evolution in the powder metallurgy N19 superalloy. The proposed full-field strategy is validated and the obtained results are in good agreement with experimental data regarding the precipitates and grain size.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

Features of the kinetics of cyclic elastoplastic deformation diagrams at dwells in cycles and superimposition of variable stresses on them

2020 ◽  
Vol 86 (12) ◽  
pp. 46-53
Author(s):  
M. M. Gadenin
Keyword(s):  
Experimental Data ◽  
Elastoplastic Deformation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Loading Cycle ◽  
Additional Variable ◽  
Dynamic Creep ◽  
Variable Stresses ◽  
Kinetics Of ◽  
Deformation Diagrams

The goal of the study is determination of the regularities of changes in cyclic strains and related deformation diagrams attributed to the existence of time dwells in the loading modes and imposition of additional variable stresses on them. Analysis of the obtained experimental data on the kinetics of cyclic elastoplastic deformation diagrams and their parameters revealed that in contrast to regular cyclic loading (equal in stresses), additional deformations of static and dynamic creep are developed. The results of the studys are especially relevant for assessing the cyclic strength of unique extremely loaded objects of technology, including nuclear power equipment, units of aviation and space systems, etc. The experiments were carried out on the samples of austenitic stainless steel under low-cycle loading and high temperatures of testing. Static and dynamic creep deformations arising under those loading conditions promote an increase in the range of cyclic plastic strain in each loading cycle and also stimulate an increase in the range of elastoplastic strain due to active cyclic deformation. At the same time the existence of dwells on extrema of stresses in cycles without imposition of additional variable stresses on them most strongly affects the growth of plastic strain ranges in cycles. Imposition of additional variable stresses on dwells also results in the development of creep strains, but their growth turns out to be somewhat less than in the presence of dwells without stresses imposed. The diagrams of cyclic deformation obtained in the experiments are approximated by power dependences, their kinetics being described in terms of the number of loading cycles using corresponding temperature-time functions. At the same time, it is shown that increase in the cyclic plastic deformation for cycles with dwells and imposition of additional variable stresses on them decreases low cycle fatigue life compared to regular loading without dwells at the same stress amplitudes, moreover, the higher the values of static and dynamic creep, the greater decrease in low-cycle fatigue life. This conclusion results from experimental data and analysis of conditions of damage accumulation for the considered forms of the loading cycle using the deformation criterion of reaching the limit state leading to fracture.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

Kinetics of the Crystallization of Potassium Sulfate

1993 ◽  
Vol 58 (8) ◽  
pp. 1848-1854 ◽  
Author(s):  
Miroslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Experimental Data ◽  
Crystal Growth ◽  
Growth Rates ◽  
Potassium Sulfate ◽  
Kinetics Of

The kinetics of the crystallization of potassium sulfate has been determined using the MSMPR technique. Values of the nucleation and crystal growth rates evaluated from the experimental data are compared with the corresponding literature data.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

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