scholarly journals Study on Vacuum Roasting Pretreatment of Carbonaceous Gold Concentrates Based on Nonoxidation Technology

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Xinwei Zhang ◽  
Yonghui Song ◽  
Ning Yin ◽  
Xinzhe Lan ◽  
Jianping Jin
Keyword(s):  
Thermal Decomposition ◽  
Carbothermic Reduction ◽  
Decomposition Reaction ◽  
Gold Content ◽  
Gold Ores ◽  
Reduction Reactions ◽  
Decomposition Reactions ◽  
Vacuum Degree ◽  
Roasting Process ◽  
Different Temperatures

Carbonaceous gold ores are difficult to treat because of the “preg-robbing” by carbonaceous matters and locking by minerals. Roasting is the most commonly used method that is useful in dealing with carbonaceous gold ores. In this study, flotation gold concentrates containing sulfides and carbonaceous matters were investigated to ascertain the reaction process and the matters’ transformation characteristics in different temperatures by vacuum roasting pretreatment. Calcine and volatile condensates were characterized with several techniques. In the process of vacuum roasting, the main chemical reactions were decomposition reaction and carbothermic reduction reactions of sulfide ores, carbothermic reduction reactions of SiO2, and thermal decomposition reactions of organic carbon. The bad effects of “preg-robbing” by carbonaceous matters were greatly weakened by the thermal decomposition and carbothermal reduction. The gold locking minerals were mainly removed by reduction reactions. The sulfides were removed in ways that did not produce SO2. The removal of sulfur and carbonaceous matters during the vacuum roasting process was 95.83% and 65.38%, respectively. Direct cyanidation of the calcine extracted from 2.13% to 88.37% of the gold content with a vacuum degree of 10 Pa and roasting from 25°C to 1,200°C for 30 min.

scholarly journals DETERMINATION OF THERMAL DECOMPOSITION REACTION CHARACTERISTICS (A, E) OF WOOD SAMPLES FOR FIRE DYNAMICS SIMULATION

2013 ◽  
Vol 1 (2) ◽  
pp. 13-24 ◽  
Author(s):  
László Beda ◽  
Attila Szabó
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Decomposition Reaction ◽  
Dynamics Simulation ◽  
Fire Dynamics ◽  
Exponential Factor ◽  
Decomposition Reactions ◽  
Reaction Characteristics ◽  
Reaction Activation Energy

Abstract The purpose of this work is to determine the pre-exponential factor (A) and the reaction activation energy (E) of decomposition reactions that are needed for Fire Dynamics Simulation (FDS) using Derivatograph Q 1500D. The materials we investigated: Pine Wood Board (PWB), Multilayered Parquet Board (MPB), Particleboard Core (PBC) and Oriented Standard Board (OSB).

Kinetic Investigation of Thermal Decomposition Reactions of Podophyllic Acid and Picropodophyllic Acid

2011 ◽  
Vol 391-392 ◽  
pp. 1230-1234
Author(s):  
Pu Hong Wen
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Model ◽  
Kinetic Parameters ◽  
Decomposition Reaction ◽  
Exponential Factor ◽  
Decomposition Reactions ◽  
Integral Forms ◽  
Free Energy Of Activation ◽  
Entropy Of Activation ◽  
Temperature Programmed

The thermal behavior and thermal decomposition kinetic parameters of podophyllic acid and picropodophyllic acid in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for leading stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analysis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was 2/3•α-1/2 for podophyllic acid and 1/2• (1-α)-1 for picropodophyllic acid. The values of Ea indicated that the reactivity of picropodophyllic acid was highter than that of podophyllic acid in the thermal decomposition reaction. The values of the entropy of activation ΔS≠, enthalpy of activation ΔH≠ and free energy of activation ΔG≠ of the reactions were estimated.

Kinetic Investigation of Thermal Decomposition Reactions of 4'-Demethypodophyllotoxin and Podophyllotoxin

2013 ◽  
Vol 800 ◽  
pp. 517-521
Author(s):  
Pu Hong Wen
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Model ◽  
Kinetic Parameters ◽  
Decomposition Reaction ◽  
Exponential Factor ◽  
Decomposition Reactions ◽  
Integral Forms ◽  
Free Energy Of Activation ◽  
Entropy Of Activation ◽  
Temperature Programmed

The thermal behavior and thermal decomposition kinetic parameters of podophyllotoxin (PPT) and 4-demethypodophyllotoxin (DMPPT) in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for leading stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analysis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of both decomposition reactions in differential form was (1-α) 2. The values of Ea indicated that the reactivity of PPT was higher than that of DMPPT in the thermal decomposition reaction. The values of the entropy of activation ΔS≠, enthalpy of activation ΔH≠ and free energy of activation ΔG≠ of the reactions were estimated.

High-temperature X-ray powder diffractometry of the decomposition of zirconium hydroxide nitrates

1993 ◽  
Vol 8 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Patricia Bénard ◽  
Jean Paul Auffrédic ◽  
Daniel Louër
Keyword(s):  
Thermal Decomposition ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Decomposition Reaction ◽  
Zirconium Hydroxide ◽  
Nitrogen Gas ◽  
X Ray ◽  
Decomposition Reactions ◽  
Unit Cells ◽  
Diffraction Patterns

The decomposition reactions of two zirconium hydroxide nitrates Zr(OH)2(NO3)2·(4+x)H2O and α-Zr(OH)2 (NO3)2·(1+x)H2O (0≤x≤1) have been studied by thermogravimetric analysis and high-temperature X-ray powder diffractometry (HTXRD), in nitrogen gas environment. The decomposition reaction sequences were clearly displayed by the HTXRD technique. They are different for the two precursors, except the formation of amorphous zirconia at low temperature (200 °C) and crystalline zirconia at about 390 °C. Three modifications of Zr(OH)2(NO3)2·H2O (α,β,γ) were identified. Their X-ray powder diffraction patterns were indexed by the successive dichotomy method. The unit cells are triclinic and present some parametric and volumetric similarities from each other and also with that of their precursor. Moreover, the thermal decomposition sequences of Zr(OH)2(NO3)2·(4+x)H2O and α-Zr(OH)2(NO3)2·(1+x)H2O include the formation of anhydrous oxide nitrate ZrO(NO3)2 and anhydrous hydroxide nitrate Zr(OH)2(NO3)2, respectively.

Non-Isothermal Decomposition Kinetic of Polypropylene/Hydrotalcite Composite

2019 ◽  
Vol 19 (11) ◽  
pp. 7493-7501 ◽  
Author(s):  
Sheng Xu ◽  
Min Zhang ◽  
Siyu Li ◽  
Moyu Yi ◽  
Shigen Shen ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Decomposition ◽  
Nitrogen Atmosphere ◽  
Heating Rates ◽  
Decomposition Reactions ◽  
Kinetic And Thermodynamic Parameters ◽  
Málek Method ◽  
Boundary Reaction ◽  
Phase Boundary Reaction ◽  
Thermal Stability Of

P3O5-10 pillared Mg/Al hydrotalcite (HTs) as a functional fire-retarding filler was successfully prepared by impregnation-reconstruction, where the HTs was used to prepare polypropylene (PP) and HTs composite (PP/HTs). Thermal decomposition was crucial for correctly identifying the thermal behavior for the PP/HTs, and studied using thermogravimetry (TG) at different heating rates. Based on single TG curves and Málek method, as well as 41 mechanism functions, the thermal decompositions of the PP/HTs composite and PP in nitrogen atmosphere were studied under non-isothermal conditions. The mechanism functions of the thermal decomposition reactions for the PP/HTs composite and PP were separately “chemical reaction F3” and “phase boundary reaction R2,” which were also in good agreement with corresponding experimental data. It was found that the addition of the HTs increased the apparent activation energy Ea of the PP/HTs comparing to the PP, which improved the thermal stability of the polypropylene. A difference in the set of kinetic and thermodynamic parameters was also observed between the PP/HTs and PP, particularly with respect to lower ΔS≠ value assigned to higher thermal stability of the PP/HTs composite.

Synthesis and Characterization of Nanocrystalline ZnO Powders by a Direct Thermal Decomposition Route Using Zinc Nitrate Hexahydrate

2013 ◽  
Vol 770 ◽  
pp. 68-71 ◽  
Author(s):  
Supphadate Sujinnapram ◽  
Uraiphorn Termsuk ◽  
Atcharawan Charoentam ◽  
Sutthipoj Sutthana
Keyword(s):  
Thermal Decomposition ◽  
Crystallization Temperature ◽  
Zinc Nitrate ◽  
Zinc Nitrate Hexahydrate ◽  
Absorption Peak ◽  
Synthesis And Characterization ◽  
Nitrate Hexahydrate ◽  
Different Temperatures ◽  
Zno Powders

The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc nitrate hexahydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 325 oC. The precursors were calcined at different temperatures of 400, 500, and 600°C for 4 h. The structure of the prepared samples was studied by XRD, confirming the formation of wurtzite structure. The synthesized powders exhibited the UV absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps were obtained to be 3.19, 3.16, and 3.14 eV for the ZnO samples thermally decomposed at 400, 500, and 600°C, respectively.

scholarly journals Carbothermic Reduction and Nitridation Mechanism of Vanadium-Bearing Titanomagnetite Concentrate

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 730
Author(s):  
Wen Yu ◽  
Xiaojin Wen ◽  
Wei Liu ◽  
Jiangan Chen
Keyword(s):  
Phase Transformation ◽  
Carbothermic Reduction ◽  
Titanium Oxides ◽  
Distribution Characteristic ◽  
Reaction Behavior ◽  
Microstructure Transformation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Roasting Process ◽  
Rate Limiting

In this study, the carbothermic reduction and nitridation mechanism of vanadium-bearing titanomagnetite concentrate are investigated in terms of phase transformation, microstructure transformation, and thermodynamic analyses. The differences in the reaction behavior of titanomagnetite and ilmenite in vanadium-bearing titanomagnetite concentrate, as well as the distribution characteristic of V in the roasted products, are emphatically studied. It is observed that the reaction sequences of titanomagnetite and ilmenite transformations into nitride are as follows: Fe3−xTixO4→Fe2TiO4→FeTiO3→M3O5→(Ti, V)(N, C); FeTiO3→M3O5→Ti(N, C). The reduction of M3O5 to TiN is the rate-limiting step of the entire reaction, and metal iron is an important medium for transferring C for the reduction of M3O5. Titanomagnetite is faster to convert into nitride than ilmenite is, and the reasons for this are discussed in detail. During the entire roasting process, V mainly coexists with Ti and seems to facilitate the conversion of titanium oxides into (Ti, V)(N, C).

scholarly journals An Experimental Study of the Decomposition and Carbonation of Magnesium Carbonate for Medium Temperature Thermochemical Energy Storage

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1316
Author(s):  
Daniel Mahon ◽  
Gianfranco Claudio ◽  
Philip Eames
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Energy Storage ◽  
Magnesium Carbonate ◽  
Experimental Results ◽  
Future Research ◽  
Medium Temperature ◽  
Different Temperatures ◽  
Decomposition Enthalpy ◽  
Co2 Atmosphere

To improve the energy efficiency of an industrial process thermochemical energy storage (TCES) can be used to store excess or typically wasted thermal energy for utilisation later. Magnesium carbonate (MgCO3) has a turning temperature of 396 °C, a theoretical potential to store 1387 J/g and is low cost (~GBP 400/1000 kg). Research studies that assess MgCO3 for use as a medium temperature TCES material are lacking, and, given its theoretical potential, research to address this is required. Decomposition (charging) tests and carbonation (discharging) tests at a range of different temperatures and pressures, with selected different gases used during the decomposition tests, were conducted to gain a better understanding of the real potential of MgCO3 for medium temperature TCES. The thermal decomposition (charging) of MgCO3 has been investigated using thermal analysis techniques including simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), TGA with attached residual gas analyser (RGA) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (up to 650 °C). TGA, DSC and RGA data have been used to quantify the thermal decomposition enthalpy from each MgCO3.xH2O thermal decomposition step and separate the enthalpy from CO2 decomposition and H2O decomposition. Thermal analysis experiments were conducted at different temperatures and pressures (up to 40 bar) in a CO2 atmosphere to investigate the carbonation (discharging) and reversibility of the decarbonation–carbonation reactions for MgCO3. Experimental results have shown that MgCO3.xH2O has a three-step thermal decomposition, with a total decomposition enthalpy of ~1050 J/g under a nitrogen atmosphere. After normalisation the decomposition enthalpy due to CO2 loss equates to 1030–1054 J/g. A CO2 atmosphere is shown to change the thermal decomposition (charging) of MgCO3.xH2O, requiring a higher final temperature of ~630 °C to complete the decarbonation. The charging input power of MgCO3.xH2O was shown to vary from 4 to 8136 W/kg with different isothermal temperatures. The carbonation (discharging) of MgO was found to be problematic at pressures up to 40 bar in a pure CO2 atmosphere. The experimental results presented show MgCO3 has some characteristics that make it a candidate for thermochemical energy storage (high energy storage potential) and other characteristics that are problematic for its use (slow discharge) under the experimental test conditions. This study provides a comprehensive foundation for future research assessing the feasibility of using MgCO3 as a medium temperature TCES material. Future research to determine conditions that improve the carbonation (discharging) process of MgO is required.

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