scholarly journals Kinetics of Pb and Zn leaching from zinc plant residue by sodium hydroxide

2015 ◽  
Vol 51 (1) ◽  
pp. 89-95 ◽  
Author(s):  
M. Erdem ◽  
M. Yurten
Keyword(s):  
Plant Residue ◽  
Core Model ◽  
Diffusion Control ◽  
Shrinking Core Model ◽  
Zinc Plant ◽  
Ash Layer ◽  
Shrinking Core ◽  
Important Amount ◽  
Increasing Demand ◽  
Kinetics Of

In the hydrometallurgical zinc production processes, important amount of hazardous solid extraction residue containing unextractable Zn and Pb is generated. Due to increasing demand of metals and the depletion of high grade natural resources, these types of wastes are gaining great importance in the metallurgical industries. In this study, selective leaching and leaching kinetics of Pb and Zn from zinc extraction residue were investigated. For this purpose; the effects of NaOH concentration, contact time, stirring speed and temperature on the Pb and Zn recovery from the residue were studied. The shrinking core model was applied to the results of the experiments. Leaching results showed that 85.55% Pb and 21.3 % Zn could be leached under the optimized conditions. The leaching of Pb and Zn were found to fit well to shrinking core model with ash layer diffusion control. Activation energy values for Pb and Zn leaching were calculated to be 13.645 and 22.59 kJ/mol, respectively.

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 Kinetics of the dissolution of sand into alkaline solutions: application of a modified shrinking core model

2004 ◽  
Vol 71 (3-4) ◽  
pp. 435-446 ◽  
Author(s):  
A Mgaidi ◽  
F Jendoubi ◽  
D Oulahna ◽  
M El Maaoui ◽  
J.A Dodds
Keyword(s):  
Core Model ◽  
Alkaline Solutions ◽  
Shrinking Core Model ◽  
Shrinking Core ◽  
Kinetics Of

CFD Simulation of Entrained Flow Gasification With Improved Devolatilization and Char Consumption Submodels

2009 ◽  
Author(s):  
Mayank Kumar ◽  
Cheng Zhang ◽  
Rory F. D. Monaghan ◽  
Simcha L. Singer ◽  
Ahmed F. Ghoniem
Keyword(s):  
Cfd Simulation ◽  
Quantitative Description ◽  
Core Model ◽  
Diffusion Control ◽  
Shrinking Core Model ◽  
Carbon Conversion ◽  
Pore Model ◽  
Shrinking Core ◽  
The Impact ◽  
Random Pore Model

In this work, we use a CFD package to model the operation of a coal gasifier with the objective of assessing the impact of devolatilization and char consumption models on the accuracy of the results. Devolatilization is modeled using the Chemical Percolation Devolitilization (CPD) model. The traditional CPD models predict the rate and the amount of volatiles released but not their species composition. We show that the knowledge of devolatilization rates is not sufficient for the accurate prediction of char consumption and a quantitative description of the devolatilization products, including the chemical composition of the tar, is needed. We incorporate experimental data on devolatilization products combined with modeling of the tar composition and reactions to improve the prediction of syngas compositions and carbon conversion. We also apply the shrinking core model and the random pore model to describe char consumption in the CFD simulations. Analysis of the results indicates distinct regimes of kinetic and diffusion control depending on the particle radius and injection conditions for both char oxidation and gasification reactions. The random pore model with Langmuir-Hinshelwood reaction kinetics are found to be better at predicting carbon conversion and exit syngas composition than the shrinking core model with Arrhenius kinetics. In addition, we gain qualitative and quantitative insights into the impact of the ash layer surrounding the char particle on the reaction rate.

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