Thermodynamic Simulation of Microarc Oxidation of Aluminum and Its Alloys in Aqueous Borate Electrolytes

2021 ◽  
Vol 50 (8) ◽  
pp. 743-753
Author(s):  
A. A. Slobodov ◽  
M. A. Markov ◽  
A. V. Krasikov ◽  
A. D. Bykova ◽  
I. N. Kravchenko ◽  
...  
Keyword(s):  
Thermodynamic Simulation ◽  
Microarc Oxidation

The solubility of calcium carbonate  in green liquor handling systems

TAPPI Journal ◽  
2019 ◽  
Vol 18 (10) ◽  
pp. 595-602
Author(s):  
ALISHA GIGLIO ◽  
VLADIMIROS G. PAPANGELAKIS ◽  
HONGHI TRAN
Keyword(s):  
Calcium Carbonate ◽  
Systematic Study ◽  
Kraft Pulp ◽  
Thermodynamic Simulation ◽  
Solubility Data ◽  
Pulp Mills ◽  
Persistent Problem ◽  
Green Liquor ◽  
Kraft Pulp Mills ◽  
Salt Systems

The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.

Thermodynamic Simulation of a Hybrid Brayton Thermosolar Plant

2016 ◽  
pp. 157-161
Author(s):  
R.P. Merchan ◽  
M.J. Santos ◽  
A. Medina ◽  
A. Calvo
Keyword(s):  
Thermodynamic Simulation

Thermodynamic Simulation of Sulphide Mineral Leaching

2009 ◽  
Vol 71-73 ◽  
pp. 437-440
Author(s):  
Lasse Ahonen ◽  
Pauliina Nurmi ◽  
Olli H. Tuovinen
Keyword(s):  
Acid Solution ◽  
Ferric Iron ◽  
Geochemical Modeling ◽  
Thermodynamic Simulation ◽  
Sulphide Mineral ◽  
Solution Ph ◽  
Dissolved Iron ◽  
Iron Precipitation ◽  
Oxidative Leaching ◽  
Mineral Leaching

Geochemical modeling program PHREEQC was used to simulate generic bioleaching processes. Carbonate minerals (e.g., calcite) dissolve in acid solution, increasing the solution pH and Ca concentration while the concentration of CO2 may be controlled by the equilibrium with the atmospheric CO2. Non-oxidative dissolution of Fe-monosulphides was demonstrated to release H2S and increase the pH. In the absence of ferric iron precipitation (goethite), the oxidation of pyrite decreased the solution pH from 2 to ~1.4, while the oxidation of Fe-monosulphide and chalcopyrite increased the solution pH to ~3.2-3.4. Assuming equilibrium precipitation of goethite, oxidative leaching decreased the solution pH for all three minerals from pH ~2 to ~0.9-1.2. Adjustment of the solution pH to 1.8 or 2.0 with KOH with concurrent equilibrium precipitation of K-jarosite resulted in low dissolved iron concentrations.

The Effect of Sodium Silicate Concentration on the Properties of the Coating Formed on Pure Zirconium by Microarc Oxidation Coating Technique

2012 ◽  
Vol 445 ◽  
pp. 637-642 ◽  
Author(s):  
Y. Gencer ◽  
M. Tarakci ◽  
S. Cengiz ◽  
K.O. Gunduz
Keyword(s):  
Surface Roughness ◽  
Sodium Silicate ◽  
Zirconium Oxide ◽  
Microarc Oxidation ◽  
Phase Content ◽  
Oxide Coatings ◽  
Silicate Concentration ◽  
X Ray ◽  
Pure Zirconium ◽  
Scanning Electron

In this study, zirconium oxide coatings were formed on pure zirconium by microarc oxidation technique with the electrolytes containing KOH and different amounts of sodium silicate (0-40 gr/lt) for the same coating duration of 2 hours. The microstructure, surface roughness, phase content and chemical composition of the coatings were characterized by using scanning electron microscopy, profilometery and X-ray diffractometry. It was found that the coatings on surface of zirconium consist of monoclinic ZrO2 (m-ZrO2) and tetragonal ZrO2 (t-ZrO2) phases and the addition and increasing sodium silicate concentration in the electrolyte increases amount of t-ZrO2 phase. The coatings were well adhered to Zr substrate with some cracks and porosities in the coating for all concentrations of sodium silicate. The coating thickness and surface roughness increased with sodium silicate concentration in the electrolyte. A glaze like Si rich structure and its increase with Si rate was evident in the outermost region of the coating.

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