scholarly journals Effect of Thickness and Compaction Degree of Overburden Soil on Radon Reduction for Uranium Tailings Reservoir

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xingwang Dai ◽  
Yifan Chen ◽  
Yan Chen ◽  
Hong Wang ◽  
Xiangyang Li ◽  
...  
Keyword(s):  
Soil Compaction ◽  
Reduction Rate ◽  
Soil Thickness ◽  
Reduction Efficiency ◽  
Increasing Trend ◽  
Increase Rate ◽  
Overburden Soil ◽  
Tailings Reservoir ◽  
Uranium Tailings ◽  
Compaction Degree

The thickness and compaction degree of the overburden soil on the beach of the uranium tailings reservoir has an important influence on the radon reduction rate. A theoretical model of radon exhalation is established and an experimental device is designed. The main results are as follows. (1) The radon reduction rate increases with the increase of thickness. When the soil compaction degree is 85.5%, 90.2%, and 94.8%, the radon reduction efficiency increases significantly when the thickness increases from 5 cm to 10 cm, and when the soil thickness is over 10 cm, the increase of radon reduction efficiency tends to be stable. When the compaction degree is 80.9%, the radon reduction rate always increases obviously with the increase of the thickness of the overburden soil, but the increase rate shows a downward trend. (2) The radon reduction rate increases gradually with the increase of compaction degree, and the increasing trend becomes less obvious when the compaction degree is more than 85.5%. Besides, the effect of the change of soil compaction on radon reduction rate decreases with the increase of soil thickness. The calculation formulas about the effect of thickness and compaction degree on radon reduction rate can guide the design and construction of radiation protection of uranium tailings reservoir.

scholarly journals Electrochemical Removal of Chromium (VI) from Wastewater

2019 ◽  
Author(s):  
Hao Peng ◽  
Yumeng Leng ◽  
Jing Guo
Keyword(s):  
Reaction Temperature ◽  
Current Density ◽  
Reduction Rate ◽  
Reduction Process ◽  
Order Equation ◽  
First Order ◽  
Chromium Vi ◽  
Reduction Efficiency ◽  
Pseudo First Order ◽  
Electrochemical Removal

Removal of hexavalent chromium had attracted much more attention as it was a hazardous contaminant. Electrochemical reduction technology was applied to removal chromium (VI) from wastewater. The mechanism and parameters affect the reduction process were investigated. The results showed that the reduction efficiency was significantly affected by the concentration of H2SO4, current density and reaction temperature. And the reduction efficiency was up to 86.45% at concentration of H2SO4 of 100g/L, reaction temperature of 70 ℃, current density at 50 A/m2, reaction time at 180 min and stirring rate of 500 rpm. The reduction process of chromium (VI) was followed pseudo-first-order equation, and the reduction rate could be expressed as Kobs = k [H2SO4]1• [j] 4•exp-4170/RT.

Evaluation of nitrate and perchlorate reduction using sulfur-based autotrophic and mixotrophic denitrifying processes

2015 ◽  
Vol 16 (1) ◽  
pp. 208-218 ◽  
Author(s):  
Deniz Uçar ◽  
Emine Ubay Çokgör ◽  
Erkan Şahinkaya
Keyword(s):  
Nitrate Reduction ◽  
Elemental Sulfur ◽  
Reduction Rate ◽  
Sulfate Concentration ◽  
Biological Reduction ◽  
Perchlorate Reduction ◽  
Guideline Value ◽  
Reduction Efficiency ◽  
Drinking Water Guideline ◽  
Denitrification Process

The biological reduction of nitrate and perchlorate was comparatively evaluated in autotrophic and mixotrophic bioreactors using elemental sulfur and/or methanol as the energy source. The mixotrophic reactor was supplemented with methanol at CH3OH/NO3−-N ratio of 1 or 1.4. The mixotrophic reactor completely reduced perchlorate in the feed up to 1,000 μg l−1. The autotrophic reactor also showed high perchlorate reduction performance and decreased perchlorate from 1,000 μg l−1 to around 33 μg l−1. Complete reduction of 25 mg NO3−-N l−1 was achieved in both reactors, corresponding to a maximum nitrate reduction rate of 300 mg NO3−-N l−1d−1 and 400 mg NO3−-N l−1d−1 in the autotrophic and mixotrophic processes, respectively. Autotrophic denitrification caused an increase of effluent sulfate concentration, which may exceed the drinking water guideline value of 250 mg l−1. In the mixotrophic denitrification process, the effluent sulfate concentration was controlled by adjusting the C/N ratio in the influent. Mixotrophic denitrification was stimulated by 25 mg l−1 methanol addition and 53% of influent nitrate was reduced by the heterotrophic process, which decreased the effluent sulfate concentration to half of the autotrophic counterpart. Therefore, the mixotrophic process may be preferred over the autotrophic process when effluent sulfate concentration is of concern and a higher perchlorate reduction efficiency is desired.

Drag reduction in turbulent flows along a cylinder by streamwise-travelling waves of circumferential wall velocity

2019 ◽  
Vol 862 ◽  
pp. 75-98 ◽  
Author(s):  
Ming-Xiang Zhao ◽  
Wei-Xi Huang ◽  
Chun-Xiao Xu
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Energy Saving ◽  
Turbulent Flows ◽  
Friction Velocity ◽  
Oscillation Amplitude ◽  
Reduction Rate ◽  
Net Energy ◽  
Centrifugal Instability ◽  
Increase Rate

Drag reduction at the external surface of a cylinder in turbulent flows along the axial direction by circumferential wall motion is studied by direct numerical simulations. The circumferential wall oscillation can lead to drag reduction due to the formation of a Stokes layer, but it may also result in centrifugal instability, which can enhance turbulence and increase drag. In the present work, the Reynolds number based on the reference friction velocity and the nominal thickness of the boundary layer is 272. A map describing the relationship between the drag-reduction rate and the control parameters, namely, the angular frequency $\unicode[STIX]{x1D714}^{+}=\unicode[STIX]{x1D714}\unicode[STIX]{x1D708}/u_{\unicode[STIX]{x1D70F}0}^{2}$ and the streamwise wavenumber $k_{x}^{+}=k_{x}\unicode[STIX]{x1D708}/u_{\unicode[STIX]{x1D70F}0}$, is obtained at the oscillation amplitude of ${A^{+}=A/u}_{\unicode[STIX]{x1D70F}0}=16$, where $u_{\unicode[STIX]{x1D70F}0}$ is the friction velocity of the uncontrolled flow and $\unicode[STIX]{x1D708}$ is the kinematic viscosity of the fluid. The maximum drag-reduction rate and the maximum drag-increase rate are both approximately 48 %, which are respectively attained at $(\unicode[STIX]{x1D714}^{+},k_{x}^{+})=$ (0.0126, 0.0148) and (0.0246, 0.0018). The drag-reduction rate can be scaled well with the help of the effective thickness of the Stokes layer. The drag increase is observed in a narrow triangular region in the frequency–wavenumber plane. The vortices induced by the centrifugal instability become the primary coherent structure in the near-wall region, and they are closely correlated with the high skin friction. In these drag-increase cases, the effective control frequency or wavenumber is crucial in scaling the drag-increase rate. As the wall curvature normalised by the boundary layer thickness becomes larger, the drag-increase region in the $(\unicode[STIX]{x1D714}^{+},k_{x}^{+})$ plane as well as the maximum drag-increase rate also become larger. Net energy saving with a considerable drag-reduction rate is possible when reducing the oscillation amplitude. At $A^{+}=4$, a net energy saving of 18 % can be achieved with a drag-reduction rate of 25 % if only the power dissipation due to viscous stress is taken into account in an ideal actuation system.

Evaluation of Drag Reduction Agent Used in Oil Pipeline Transportation

2012 ◽  
Vol 217-219 ◽  
pp. 153-156 ◽  
Author(s):  
Zhi Wu He ◽  
Ning Jun Li ◽  
Zhen Yun Zhang ◽  
Hui Li Yang ◽  
Ai Jun Wei
Keyword(s):  
Drag Reduction ◽  
Reduction Rate ◽  
Pipeline Transportation ◽  
Oil Pipeline ◽  
Test Loop ◽  
Increase Rate

This article describes the principles and methods of evaluating DRA in the lab, then evaluate the effect of DRA in the lab by designing a DRA test loop. This is measure that thoes DRA difference concentration be provided with flow increase rate and Drag reduction rate in test loop.

Multiple Compaction Tests on Laterite

2013 ◽  
Vol 405-408 ◽  
pp. 138-141
Author(s):  
Rui Ying Wang ◽  
Qing Wang ◽  
Ying Gao ◽  
Shuo Chao Bao ◽  
Zheng Wei Li ◽  
...  
Keyword(s):  
Moisture Content ◽  
Soil Compaction ◽  
Physical Nature ◽  
High Strength ◽  
Optimum Moisture Content ◽  
Dry Density ◽  
High Plasticity ◽  
Maximum Dry Density ◽  
Engineering Projects ◽  
Compaction Degree

Laterite has high void ratio, low density, high moisture content, high plasticity, but it does not match with their physical nature, which has the relatively high strength and low compressibility. In order to improve the strength of laterite and increase its compactness, we usually use the method of dynamic compaction in some large engineering projects. Its easy to find that soil compaction degree increased with the moisture content When the content of moisture is low, but soil compaction decreased after reaching the highest. Multiple compaction can effectively improve the maximum dry density and reduce optimum moisture content, but after compaction number is too much that optimum moisture content dont increase obviously.

Numerical analysis of the soil compaction degree under multi-location tamping

2017 ◽  
Vol 22 (4) ◽  
pp. 417-433 ◽  
Author(s):  
Wei Wang ◽  
Jinzhong Dou ◽  
Jinjian Chen ◽  
Jianhua Wang
Keyword(s):  
Numerical Analysis ◽  
Soil Compaction ◽  
Compaction Degree
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