Decomposition of Ilmenite by Ammonium Hydroxide

2013 ◽  
Vol 813 ◽  
pp. 484-488
Author(s):  
Hai Bo Tang ◽  
Yu Min Liu
Keyword(s):  
Experimental Data ◽  
Reaction Temperature ◽  
Significant Influence ◽  
Hydrothermal Process ◽  
Ammonium Hydroxide ◽  
Core Model ◽  
Shrinking Core Model ◽  
Operating Variables ◽  
New Process ◽  
Shrinking Core

A new process was provided for decomposition of ilmenite by ammonium hydroxide under hydrothermal process. The significant effects of reaction temperature, NH4OH concentration, NH4OH-to-ilmenite mass ratios on titanium extraction were studied. The temperature showed significant influence on titanium extraction. The experimental data of the extraction rates under the relevant operating variables were well interpreted with the shrinking core model under chemically controlled process.

scholarly journals Kinetic Study of Selective Chlorination of Iron in Ilmenite Ore

2020 ◽  
Vol 321 ◽  
pp. 07009
Author(s):  
So-Yeong Lee ◽  
Sung-Hun Park ◽  
Ho-Sang Sohn
Keyword(s):  
Chemical Reaction ◽  
Reaction Temperature ◽  
Reaction Rate ◽  
Product Layer ◽  
Fixed Bed Reactor ◽  
Core Model ◽  
Shrinking Core Model ◽  
Selective Chlorination ◽  
Chlorine Gas ◽  
Shrinking Core

The selective chlorination of ilmenite with coke and chlorine gas was conducted in the fixed bed reactor and effects of coke content and reaction temperature on reaction rate were investigated. In particular, the chlorination rate of iron in ilmenite was simulated by the unreacted shrinking core model. The reaction rate was simulated by calculating the chlorine gas consumption rate as the unreacted core shrinks. In addition, each of reaction resistances that chemical reaction at the reaction interface, diffusion through the product layer, and boundary film mass transfer resistances were calculated. The simulated reaction rates were in good agreement with the experimental results and the rate controlling step changed as the chlorination reaction progressed. Furthermore, the diffusion resistance through the product layer was dominant at lower reaction temperature, whereas the chemical reaction was dominant as the reaction temperature increased. It is because the diffusion of chlorine gas through the product layer could be hindered at lower reaction temperatures. Key words: Ilmenite, Selective chlorination, Synthetic rutile, Shrinking core model

scholarly journals Studi Kinetika Proses Atmospheric Pressure Acid Leaching Bijih Laterit Limonit Menggunakan Larutan Asam Nitrat Konsentrasi Rendah

2018 ◽  
Vol 12 (2) ◽  
pp. 19
Author(s):  
Kevin Cleary Wanta ◽  
Felisha Hapsari Tanujaya ◽  
Ratna Frida Susanti ◽  
Himawan Tri Bayu Murti Petrus ◽  
Indra Perdana ◽  
...  
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Nitric Acid ◽  
Atmospheric Pressure ◽  
Acid Leaching ◽  
Operating Conditions ◽  
Core Model ◽  
Shrinking Core Model ◽  
Shrinking Core ◽  
Pressure Acid Leaching

A B S T R A C TKinetics study of atmospheric pressure acid leaching (APAL) process is indispensable for extractor design in an industrial scale. So far, the kinetic model used for this process is the shrinking core model. In this study, the shrinking core model was evaluated against experimental data for laterite leaching process using a solution of low concentration nitric acid (0.1 M). Variations in temperature and particle size were carried out at 303–358 K and <75–250 microns. Other operating conditions, such as pulp density, stirring speed, and time were kept at 20% w/v, 200 rpm, and 120 minutes, respectively. The model evaluation results showed that the shrinking core model was not suitable for this process because the process controlling stage is not just one stage only.Keywords: kinetics; laterite; leaching; shrinking core.A B S T R A KStudi terkait kinetika proses atmospheric pressure acid leaching (APAL) sangat diperlukan untuk proses perancangan ekstraktor dalam skala industri. Selama ini, model kinetika yang digunakan untuk proses tersebut adalah model shrinking core. Dalam studi ini, model shrinking core dievaluasi terhadap data percobaan proses leaching bijih laterit dengan menggunakan larutan asam nitrat konsentrasi rendah, 0,1 M. Variasi suhu dan ukuran partikel dilakukan pada 303–358 K dan <75–250 mikron. Kondisi operasi lainnya, seperti densitas pulp, kecepatan pengadukan, dan lama proses dijaga tetap pada 20%b/v, 200 rpm, dan 120 menit, secara berurutan. Hasil evaluasi model menunjukkan bahwa model shrinking core tidak cocok untuk proses ini karena tahapan pengendali proses tidak hanya satu tahapan saja.Kata kunci: kinetika; laterit; leaching; shrinking core

scholarly journals An alternative method to determine the diffusion coefficient for the shrinking core model

2011 ◽  
Vol 13 (2) ◽  
pp. 54-56 ◽  
Author(s):  
Sylwia Kwiatkowska-Marks ◽  
Marek Wójcik ◽  
Leonard Kopiński
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficient ◽  
Numerical Methods ◽  
Analytical Solution ◽  
Copper Ions ◽  
Effective Diffusion ◽  
Core Model ◽  
Shrinking Core Model ◽  
Alternative Method ◽  
Shrinking Core

An alternative method to determine the diffusion coefficient for the shrinking core model A new method to determine the effective diffusion coefficient of sorbate in sorbent granule based on the analytical solution of the shrinking core model (SCM) has been proposed. The experimental data presented by Lewandowski and Roe1 concerning the sorption of copper ions by alginate granules have been applied to compare the analytical and numerical methods. The results obtained by both methods are very close.

scholarly journals Correction to An Unreacted Shrinking Core Model Serves for Predicting Combustion Rates of Organic Additives in Clay Bricks

2021 ◽  
Vol 35 (5) ◽  
pp. 4616-4616
Author(s):  
Florian Wesenauer ◽  
Christian Jordan ◽  
Mario Pichler ◽  
Aron Frei ◽  
Mudassar Azam ◽  
...  
Keyword(s):  
Core Model ◽  
Shrinking Core Model ◽  
Organic Additives ◽  
Clay Bricks ◽  
Shrinking Core

Mesopores inside electrode particles can change the Li-ion transport mechanism and diffusion-induced stress

2010 ◽  
Vol 25 (8) ◽  
pp. 1433-1440 ◽  
Author(s):  
Stephen J. Harris ◽  
Rutooj D. Deshpande ◽  
Yue Qi ◽  
Indrajit Dutta ◽  
Yang-Tse Cheng
Keyword(s):  
Core Model ◽  
Published Data ◽  
Shrinking Core Model ◽  
Stress Distributions ◽  
Active Electrode ◽  
Free Surfaces ◽  
Surface Cracking ◽  
Active Particles ◽  
Shrinking Core ◽  
And Diffusion

Following earlier work of Huggins and Nix [Ionics6, 57 (2000)], several recent theoretical studies have used the shrinking core model to predict intraparticle Li concentration profiles and associated stress fields. A goal of such efforts is to understand and predict particle fracture, which is sometimes observed in degraded electrodes. In this paper we present experimental data on LiCoO2 and graphite active particles, consistent with previously published data, showing the presence of numerous internal pores or cracks in both positive and negative active electrode particles. New calculations presented here show that the presence of free surfaces, from even small internal cracks or pores, both quantitatively and qualitatively alters the internal stress distributions such that particles are prone to internal cracking rather than to the surface cracking that had been predicted previously. Thus, the fracture strength of particles depends largely on the internal microstructure of particles, about which little is known, rather than on the intrinsic mechanical properties of the particle materials. The validity of the shrinking core model for explaining either stress maps or transport is questioned for particles with internal structure, which includes most, if not all, secondary electrode particles.

scholarly journals Macerals of Shengli Lignite in Inner Mongolia of China and Their Combustion Reactivity

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Ying Yue Teng ◽  
Yu Zhe Liu ◽  
Quan Sheng Liu ◽  
Chang Qing Li
Keyword(s):  
Activation Energy ◽  
Homogeneous Model ◽  
Optical Microscope ◽  
Core Model ◽  
Shrinking Core Model ◽  
Compact Structure ◽  
Shrinking Core ◽  
Combustion Reactivity ◽  
Combustion Processes ◽  
Kinetics Of

The macerals, including fusinitic coal containing 72.20% inertinite and xyloid coal containing 91.43% huminite, were separated from Shengli lignite using an optical microscope, and their combustion reactivity was examined by thermogravimetric analysis. Several combustion parameters, including ignition and burnout indices, were analyzed, and the combustion kinetics of the samples were calculated by regression. Fusinitic coal presented a porous structure, while xyloid coal presented a compact structure. The specific surface area of fusinitic coal was 2.5 times larger than that of xyloid coal, and the light-off temperature of the former was higher than that of the latter. However, the overall combustion reactivity of fusinitic coal was better than that of xyloid coal. The combustion processes of fusinitic and xyloid coals can be accurately described by both the homogeneous model and the shrinking core model. The features of xyloid coal agree with the shrinking core model when its conversion rate is 10%–90%. The activation energy of fusinitic coal during combustion can be divided into three phases, with the middle phase featuring the highest energy. The activation energy of xyloid coal is lower than that of fusinitic coal in the light-off phase, which may explain the low light-off temperature of this coal.

scholarly journals Kinetic Study in Atmospheric Pressure Organic Acid Leaching: Shrinking Core Model versus Lump Model

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 613
Author(s):  
Kevin Cleary Wanta ◽  
Widi Astuti ◽  
Indra Perdana ◽  
Himawan Tri Bayu Murti Petrus
Keyword(s):  
Citric Acid ◽  
Acid Solution ◽  
Acid Leaching ◽  
Core Model ◽  
Shrinking Core Model ◽  
Citric Acid Solution ◽  
Lumped Model ◽  
Leaching Process ◽  
Shrinking Core ◽  
Simulation Results

The kinetics study has an essential role in the scale-up process because it illustrates the real phenomena of a process. This study aims to develop a mathematical model that can explain the mechanism of the leaching process of laterite ore using a low concentration of the citric acid solution and evaluate that model using the experimental data. As a raw material, this process used powder-shaped limonite laterite ores with a size of 125–150 µm. The leaching process is carried out using 0.1 M citric acid solution, F:S ratio of 1:20, and a leaching time of 2 h. The temperature parameter was varied at 303, 333, and 358 K. The experimental results showed that the higher the operating temperature, the higher the extracted nickel. The results of this experiment were used to evaluate the shrinking core kinetics model and the lumped model. The simulation results for both models show that the lumped model can provide better simulation results. Quantitatively, the percentage of errors from the shrinking core model is around 3.5 times greater than the percentage of errors from using the lumped model. This result shows that in this leaching process, the process mechanism that occurs involves the reactant diffusion step and the chemical reactions step; those steps run simultaneously.

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