According to formula (1), m=Sv D t=Sk D ΔCt=k D S(C 0 -C i )t (1)

According to relevant factors, several mass transfer rate equations can be listed one by one.

Where k m and k' m . They can all be called mass transfer coefficients, but their use conditions are different. The dimensions or factors are different, and their values ​​are obviously different. Therefore, when using the experimental data to calculate the mass transfer coefficient, we must consider the characteristics of each specific case and pay attention to the unit uniformity.

In heap leaching, the mass transfer equation is generally used to establish the relationship between the concentration C of the metal leaching and leaching time t, the relationship between the amount of metal or leaching of time t. When the leaching solution flows through the ore heap at a constant spray intensity, its volume (V) is divided into time.

Or dV=QdtS (4A)

Where, the cross-sectional area of ​​the S-mine heap, m 2 ;

Spray intensity in Q-heap leaching, m 3 /(h·m 2 );

The average concentration of metal in the solution during the C-leaching time Δt, kg/m 3 .

We define the leaching metal concentration C as the differential of the amount of leaching metal to the volume of the leaching solution flowing through the heap, ie

Substituting the formula (4A) into the formula (4B),

Finishing (4C) and integrating, get

â–³m=k" m QCSâ–³t (5)

Where, k"m-mass transfer coefficient during heap leaching;

Δm-the leaching time Δt, the amount of metal leached per unit area, kg.

Comparing k m , k' m and k" m in equations (2), (3) and (5), it is known that the use of mass transfer coefficients is based on the conditions of use. The values ​​and the factors are also different depending on the conditions.

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