B. Calculation of clarification distance of tailings In the process of tailings hydraulic alluvial, fine-grained tailings enter the tailings pond with the slurry water, and need to stay in the water for a certain period of time (flowing a certain distance - clearing distance) to sink the fine particles. The tailings water can be clarified to reach a certain water quality standard. The calculation of the clarification distance is calculated according to Figure 2, using Equation 4.
Where l—the required clarification distance, m;
h l ———The depth of the particles sinking in still water (ie the thickness of the clarified water layer), generally not less than 0.5~1.0m, depending on the overflow depth of the overflow, the requirement that h 1 is greater than the overflow head of the overflow, m;
υ———average flow rate, m/s;
Q—the flow rate of the slurry, m 3 /s;
h 2 ———the average depth of slurry flow, generally taken as 0.5 to 1.0 m;
n———The number of ore discharges working at the same time depends on the diameter of the discharge pipe and the dispersion pipe (supervisor). The sum of the cross-sectional areas of the discharge pipes required to work at the same time is equal to twice the cross-sectional area of ​​the dispersion pipe.
a———The spacing of the discharge pipe is generally 5~15m.
u———Settling velocity of particles in still water, m/s; refer to the relevant professional data to calculate or look up the value according to the formula. The formula calculation method is introduced here. First, the flow state to which it belongs should be discriminated, and then calculated according to the formula.
Where u———particle sedimentation velocity, m/s;
γ g ———solid particle density, t/m 3 ;
d————the minimum particle diameter of the interception, m;
υ———The viscosity coefficient of clear water movement, m 2 /s.[next]
The most important factor in determining the level of accumulation of C final to determine the final tailings accumulation elevation field is the total amount of tailings beneficiation plants discharge in the production and service period, or the total amount by mine tailings ore reserves calculation of the required storage capacity. The final accumulation elevation of the tailings field is determined by the geometric storage capacity curve, and the stacking plan is drawn (see Figure 3), followed by the flood control calculation, the seepage calculation and the clarification distance calculation. If the requirements of the following three conditions are met, the initial elevation is determined. fulfil requirements.
(1) Meet the requirements of backwater storage water depth hj, flood depth ht, safety super high e:
(H m -H k )≥(h j +h t +e) (8)
Where H m is the final stacking height of the tailings, m;
H k ——— control the water level of the tailings pond, m;
h j ——— Backwater storage water depth, m;
h t ——— adjust the flood depth, m;
e———The safety of flood control in tailings is super high, m.
(2) Meet the requirements of tailing water clarification distance. When controlling the water level, the minimum distance Lh from the sedimentary waterline to the overflow should be:
L k ≥(L+L 3 ) (9)
Where L——— is the clarification distance, m;
L 3 --- to reach the average flowing water layer thickness h 2 of the tailings slurry;
(3) The requirement of the minimum sedimentation beach length L 1 for seepage control. In order to ensure the stability of the tailings accumulation dam, the height of the immersion line and the seepage slope of the dam should be controlled. The maximum length of the sedimentation shoal when the maximum flood level of the seepage control condition is met should meet the minimum sedimentation length L 1 proposed by the design of the large dry slab.
If one of the above three conditions does not meet the requirements, the final stacking height should be increased until the requirements are met.
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