scholarly journals Feasibility of Recycling Bayer Process Red Mud for the Safety Backfill Mining of Layered Soft Bauxite under Coal Seams

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 722
Author(s):  
Shuai Li ◽  
Rui Zhang ◽  
Ru Feng ◽  
Boyi Hu ◽  
Guojun Wang ◽  
...  
Keyword(s):  
Red Mud ◽  
Simulation Analysis ◽  
Creep Damage ◽  
Cementitious Materials ◽  
In Situ Stress ◽  
Bayer Process ◽  
Coal Seams ◽  
Backfill Mining ◽  
Damage Process ◽  
Pressure Stress

The mining of layered soft bauxite under coal seams (BCS) will cause serious underground goaf disasters and surface Bayer process red mud (BRM) pollution. In order to realize the safe and efficient mining of BCS, the feasibility of recycling BRM as a backfilling aggregate was explored. A series of tests were conducted to prevent the pollution diversion of BRM from surface storage to underground goafs, and a numerical simulation analysis of the backfilling mining process was carried out based on FLAC3D to protect the overlying coal seam. The results show that: under the action of encapsulation, solidification and inhibiting precipitation from cementitious materials, the leaching concentration of harmful substances in red mud-based cemented backfill (RCB) can be reduced 70% more than fresh BRM. Mining disturbance redistributes the in-situ stress field of overlying strata; normal backfilling can not only reduce the pressure stress of pillars, but also release the tensile stress in the roof and floor from +0.4956 MPa to −0.1992 MPa, effectively preventing roof subsidence. Since the creep damage process of past backfill will absorb and dissipate lots of energy, the disturbance range caused by backfill mining is controlled within 3 m, which is only 10% of the open-stope method.

Atomic Diffusion Induced Damage of Ni-Base Super Alloy at Elevated Temperature

2016 ◽  
Author(s):  
Motoki Takahashi ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Power Plants ◽  
Creep Damage ◽  
Rotor Blades ◽  
Atomic Scale ◽  
Atomic Diffusion ◽  
Kernel Average Misorientation ◽  
Damage Process ◽  
Creep Loading ◽  
Ebsd Method ◽  
Base Superalloy

Ni-base superalloys consisting of binary phases such as cuboidal γ’ (Ni3Al) precipitates orderly dispersed in the γ matrix (Ni-rich matrix) have been generally used for rotor blades in energy power plants. However, fine dispersed γ’ precipitates are coarsened perpendicularly to the applied load direction during high temperature creep loading. As this phenomenon called “Rafting” proceeds, the strengthened micro texture disappears and then, cracks starts to grow rapidly along the boundaries of the layered texture. Thus, it is very important to evaluate the change of the crystallinity of the alloy in detail for explicating the atomic scale damage process. In this study, the change of the micro-texture of the Ni-base superalloy (CM247LC) was observed by using EBSD method. The change in the crystallinity was evaluated using both Kernel Average Misorientation (KAM) and image quality (IQ) values. The KAM value indicates the dislocation density and the IQ value shows the order of atom arrangement in the observed area. As a result, KAM value showed no significant change with increasing the creep damage. On the other hand, the IQ value monotonically shifted to lower values and the average IQ value gradually decreased as the creep loading time increased. Decreasing IQ value without change in KAM value implies that the density of point defects such as vacancies mainly increased under creep loading and ordered Ll2 structure became disordered. Therefore, the creep damage of this alloy is mainly dominated by not the accumulation of dislocations, but the increase in the disorder of atom arrangement in the micro texture caused by the diffusion of component elements.

scholarly journals Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

scholarly journals The Creep-Damage Model of Salt Rock Based on Fractional Derivative

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2349 ◽  
Author(s):  
Hongwei Zhou ◽  
Di Liu ◽  
Gang Lei ◽  
Dongjie Xue ◽  
Yang Zhao
Keyword(s):  
Fractional Derivative ◽  
Creep Test ◽  
Damage Model ◽  
Creep Damage ◽  
Uniaxial Stress ◽  
Radioactive Waste Disposal ◽  
Creep Process ◽  
Salt Rock ◽  
Damage Process ◽  
Creep Damage Model

The use of salt rock for underground radioactive waste disposal facilities requires a comprehensive analysis of the creep-damage process in salt rock. A computer-controlled creep setup was employed to carry out a creep test of salt rock that lasted as long as 359 days under a constant uniaxial stress. The acoustic emission (AE) space-time evolution and energy-releasing characteristics during the creep test were studied in the meantime. A new creep-damage model is proposed on the basis of a fractional derivative by combining the AE statistical regularity. It indicates that the AE data in the non-decay creep process of salt rock can be divided into three stages. Furthermore, the authors propose a new creep-damage model of salt rock based on a fractional derivative. The parameters in the model were determined by the Quasi-Newton method. The fitting analysis suggests that the new creep-damage model provides a precise description of full creep regions in salt rock.

Red Mud Flocculants Used in the Bayer Process

2013 ◽  
pp. 425-430
Author(s):  
F. Ballentine ◽  
M. E. Lewellyn ◽  
S. A. Moffatt
Keyword(s):  
Red Mud ◽  
Bayer Process

scholarly journals FLAC3D Simulation Analysis of the Extended Height of the Water-induced Fracture Zone in Different Coal Seams

2018 ◽  
Vol 170 ◽  
pp. 022034
Author(s):  
Yanhao Chen ◽  
Qian Yu ◽  
Yukun Cao ◽  
Tingyuan Ye ◽  
Jianyuan Zhang
Keyword(s):  
Fracture Zone ◽  
Simulation Analysis ◽  
Coal Seams

High Temperature Damage of Ni-Base Superalloy Caused by the Change of Microtexture due to the Strain-Induced Anisotropic Diffusion of Component Elements

2011 ◽  
Author(s):  
Hideo Miura ◽  
Ken Suzuki ◽  
Yamato Sasaki ◽  
Tomohiro Sano ◽  
Naokazu Murata
Keyword(s):  
High Temperature ◽  
Anisotropic Diffusion ◽  
Axial Strain ◽  
Creep Damage ◽  
Face Centered Cubic ◽  
Directional Coarsening ◽  
Damage Process ◽  
Temperature Damage ◽  
Face Centered ◽  
Base Superalloy

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. Since the micro texture of the gamma-prime (γ′) phase was found to vary during the creep damage process, it is possible, therefore, to evaluate the creep damage of this material quantitatively by measuring the change of the micro texture. The mechanism of the directional coarsening of γ′ phasesof Ni-base superalloy under uni-axial strain at high temperatures, which is called rafting, was analyzed by using molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the finely dispersed γ/γ′ interface in the superalloy was observed clearly in a Ni(001)/Ni3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin films structures which consisted of the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Both palladium and tantalum were effective elements which restrain Al atoms from moving around the interface under the applied stress, while titanium and tungsten accelerated the strain-induced anisotropic diffusion, and thus, the rafting phenomenon.

Effect of Calcined Red Mud Addition on the Hydration of Portland Cement

2012 ◽  
Vol 727-728 ◽  
pp. 1408-1411 ◽  
Author(s):  
Daniel Véras Ribeiro ◽  
João A. Labrincha ◽  
Márcio Raymundo Morelli
Keyword(s):  
Portland Cement ◽  
Red Mud ◽  
Setting Time ◽  
Cementitious Materials ◽  
Adiabatic Calorimeter ◽  
Hydration Process ◽  
Early Hydration ◽  
Bauxite Ore ◽  
Calorimetric Studies ◽  
Reference Mixture

The red mud (RM) is a solid waste derived from the processing of bauxite ore to produce alumina and it is considered a hazardous waste due to its high pH. This paper describes the use of mud untreated and after calcination at distinct temperatures (450, 650, and 1000°C) attempting to improve its reactivity. The Portland cement was replaced up to 30 wt% red mud, and its addition changed the hydration process, evaluated by calorimetric studies of early hydration and setting time. By comparing with the reference mixture (without red mud), the obtained results confirm the potential of the red mud to be used as pozzolanic additive to cementitious materials. Temperature of hydration was monitored by a quasi-adiabatic calorimeter (Langavant). The hydration temperature increases with RM addition, particularly if calcined in the same interval (450-650°C). In this condition, the hydration process is accelerated.

scholarly journals Effect of red mud addition on the corrosion parameters of reinforced concrete evaluated by electrochemical methods

2012 ◽  
Vol 5 (4) ◽  
pp. 451-467 ◽  
Author(s):  
D.V. Ribeiro ◽  
J.A. Labrincha ◽  
M.R. Morelli
Keyword(s):  
Electrical Resistivity ◽  
Reinforced Concrete ◽  
Red Mud ◽  
Corrosion Potential ◽  
Corrosion Process ◽  
Bayer Process ◽  
Alumina Production ◽  
High Ph ◽  
High Electrical Resistivity ◽  
Bauxite Ore

Red mud, the main waste generated in aluminum and alumina production from bauxite ore by the Bayer process, is considered "hazardous" due to its high pH. The high pH also provides greater protection of rebars, which is reflected in the low corrosion potential and high electrical resistivity (filler effect) of concrete. The corrosion potential was monitored by electrochemical measurements and the electrical resistivity was evaluated using sensors embedded in concrete test specimens. The results showed that the addition of red mud is beneficial to concrete, reducing its corrosion potential and increasing its electrical resistivity. Red mud proved to be a promising additive for concrete to inhibit the corrosion process.

OS0804 EBSD Observation and Strain Evaluation on Creep Damage Process of SUS304HTB Steel

2012 ◽  
Vol 2012 (0) ◽  
pp. _OS0804-1_-_OS0804-3_
Author(s):  
Yoshiki MIZUTANI ◽  
Kazunari FUJIYAMA ◽  
Hirohisa KIMACHI
Keyword(s):  
Creep Damage ◽  
Damage Process
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