scholarly journals Shear-Dependent Yield Stress of Iron Ore Fine Tailings in Two-Step Flocculation Process

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ying Yang ◽  
Hongjiang Wang ◽  
Bern Klein ◽  
Aixiang Wu
Keyword(s):  
Fractal Dimension ◽  
Yield Stress ◽  
Network Structure ◽  
Iron Ore ◽  
Shear Resistance ◽  
Strength Factor ◽  
Floc Size ◽  
Fine Tailings ◽  
Floc Strength ◽  
Flocculation Process

Both shear and flocculation have a significant influence on the rheological behavior of tailings, especially the yield stress. In the two-step flocculation process, the above two kinds of actions exist at the same time, and they influence each other. In order to explore the change rule of the yield stress and its internal causes, a two-step flocculation process of the iron ore fine tailings with different shear conditions in the four different phases was designed. In the primary flocculation phase, tailing particles combined with the primary flocculant and formed a primary floc network structure. In the primary broken phase, shear destroyed the primary floc network structure and decreased the average floc size, so the shear-dependent yield stress, the floc strength factor, and the fractal dimension decreased. In the secondary flocculation phase, broken floc combined with the secondary flocculant and produced a more compact floc network structure which had a better shear resistance. Therefore, in the secondary broken phase, with the increase of shear, the decrease of yield stress, the floc strength factor, and fractal dimension were less obvious than that in the primary broken phase. In both two broken phases, the yield stress of the secondary flocculating slurry was always higher than that of the primary flocculating slurry, but with the increase of shear, the difference became smaller. The floc strength and fractal dimension also showed the same rule. The internal reasons for the stronger shear resistance of the secondary flocculating slurry were the increase of the number of binding sites, the electric neutralization between the two flocculants, and the steric hindrance effect of the flocculants.

Investigation of the mechanism for selective flocculation process using natural iron ore tailings

2020 ◽  
Vol 117 (1) ◽  
pp. 102
Author(s):  
Lopamudra Panda ◽  
Surendra Kumar Biswal ◽  
Rayasam Venugopal ◽  
Narayan R. Mandre
Keyword(s):  
Ultrafine Particles ◽  
Iron Ore ◽  
Gangue Mineral ◽  
Ftir Analysis ◽  
Selective Flocculation ◽  
Iron Ore Tailings ◽  
Natural Iron ◽  
The Government ◽  
Zeta Potential Analysis ◽  
Flocculation Process

A huge quantity of iron ore tailings was generated every year from the iron ore washing plants during beneficiation. These discarded tailings were stored in the tailing pond. Safe storage and handling of these tailings are a major concern to the management. Due to depletion of high-grade ore, the government of India had reduced the cut-off grade from 55 to 45% because of the shortage of the iron ore reserves. Ultrafine particles present in the tailings cannot be treated effectively by the conventional methods due to particle size limitations. For Indian iron ore, associated gangue mineral alumina is the major source which causes problems in the blast furnace. Removal of alumina from the iron ore of ultrafine size is a hill task. A selective flocculation approach was employed to the iron ore tailings which contain 50.98% of Fe (T) with 8.86% of Al2O3 assay. It was observed that, when applying a selective flocculation process, the concentrate contains more than 63.48% Fe (%), 2.5% Al2O3 with 31.196% recovery (%). The mechanism was investigated using zeta potential analysis, FTIR analysis, etc.

The effects of starvation on physical characteristics of flocs in SBR for treating saline wastewater

2007 ◽  
Vol 56 (7) ◽  
pp. 41-46 ◽  
Author(s):  
Sang-Soo Kim ◽  
Byung-Hyun Moon ◽  
Gyu-Tae Seo ◽  
Cho-Hee Yoon
Keyword(s):  
Fractal Dimension ◽  
Size Distribution ◽  
Physical Characteristics ◽  
Time Response ◽  
Saline Wastewater ◽  
Floc Size ◽  
N Removal ◽  
Removal Efficiencies ◽  
P Removal

This study focused on the effects of starvation on physical characteristics of flocs in SBR for treating saline wastewater. Feeding was stopped for 5 and 15 days. A time response of the floc to these starvation periods was monitored as well as the removal efficiencies of pollutants. Correlation between the physical characteristics of flocs and settling of sludge was conducted. As the starvation periods were increased, there was a shift in the floc size distribution from a high proportion of large flocs to the development of small size flocs. The fractal dimension of flocs also decreased, as starvation periods were increased. From the results, the effect of starvation on SBR treating saline wastewater can be ordered as follows: CODMn removal < floc size and fractal dimension < T-N removal < T-P removal.

Pure Material Instability and the Concept of Yield Stress

1999 ◽  
Vol 9 (2) ◽  
pp. 58-63 ◽  
Author(s):  
Corneliu Balan
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Network Structure ◽  
Flow Curve ◽  
Constitutive Relations ◽  
Structural Instability ◽  
Pure Material ◽  
Viscous Liquids ◽  
Internal Network ◽  
Constant Shear Stress

Abstract The paper is concerned with the rheological study of gels, complex materials which are characterised by an internal network structure developed in viscous liquids. This category of materials exhibits in viscometric motion a yield state at a critical value of the applied shear stress. The yield shear stress defines the plateau behaviour in the steady flow curve. The creeping experiments and the dynamics of the Oldroyd’s 3 constants model put in evidence the connection between the loss of stability of the network structure and the coexisting strain rates at a constant shear stress. The correlation between theory, numerical simulations and experiments are established. All the results are qualitatively consistent with the statement that the concept of yield stress is ’natural defined‘ in the context of the pure material (structural) instability (i.e. instability at zero Reynolds number) of constitutive relations with non-monotone flow curve.

scholarly journals Beyond 5G Network Architecture Study: Fractal Properties of Access Network

2020 ◽  
Vol 10 (20) ◽  
pp. 7191
Author(s):  
Alexander Paramonov ◽  
Ammar Muthanna ◽  
Omar I. Aboulola ◽  
Ibrahim A. Elgendy ◽  
Riad Alharbey ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Communication Networks ◽  
Network Structure ◽  
Network Architecture ◽  
Access Network ◽  
Numerical Characteristic ◽  
Radio Waves ◽  
Efficient Manner ◽  
Network Connection ◽  
Fractal Properties

Wireless networks connect various devices through radio waves in which the network connection may have different structures. Moreover, the network structure is determined based on the placement areas of the network elements, which can be affected by the building and their locations. However, the numerical characteristic which describe the features of the real environment and allow them to be related to the properties of the model are still a challenge that has not been well addressed. To this end, in this paper, we analyze the modeling problems related to the structure of user placement in the access network. Our proposed solution is based on a description of the user environment structure in which cities in the form of buildings and constructions are considered as a typical environment. We propose a new model for addressing the wireless network structure in an efficient manner in which the features of the environment are considered, which are numerically expressed in the form of the Hurst parameter or fractal dimension. In addition, the fractal dimension, geometric fractals, and the characteristics of the user’s distribution territory and urban development are efficiently utilized. Then, we analyze the influence of the fractal properties of the environment on the structure of promising communication networks; in particular, on the structure of the Internet of Things network. Finally, simulation results proved that the proposed model is considered as a beneficial solution for modeling mobile communication and wireless access networks, including fifth-generation networks.

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