Mathematical expression of heap leaching rate - Jack Busson expression

Since the Taylor expression does not reflect the relationship between the unsaturated flow parameters and the leaching rate, Jack Busson et al. believe that the Taylor type is unlikely to explain the leaching mechanism, and thus it is impossible to guide the research and production of heap leaching.

Jack Busson's experimental setup is shown in Figure 1. The device features a immersion column placed on a continuous weighing device with multiple vents to prevent air from being compressed or retained. The experiment was carried out with a constant spray intensity.

Figure 1 Large column leaching test device

The unsaturated flow parameters are obtained by the following relationship:

Se= (1)

e= (2)

Wherein the amount of wet ore in the W w -column flow in the unit area and the flow rate of the outflowing leachate are equal;

W d - dry ore amount;

W a - the amount of ore completely saturated with the leaching solution;

Ore volume density in ρb-column;

Ρb-soluble solution density;

The saturation of the ore medium tested by Se-;

The porosity of the ore in the e-column.

It should be noted that the experimental device proposed by Jack Busson and the adaptability of the formulas (1) and (2) are also conditional. The various expressions proposed by Jack Busson et al. are only applicable to heap leaching of fine-grained ores. For ore heap leaching greater than 12.5 mm, it is still difficult to use. In addition, when the above apparatus is used for the test, the initial flow rate should not be too large, otherwise a more accurate value of the porosity e and the saturation S e cannot be obtained. In fact, such tests and formulas are primarily used to find suitable apparent immersion fluid flow rates or spray strengths.

Now suppose that the porosity e, saturation S e of the ore in the column is obtained experimentally, and the average maximum apparent flow velocity is given by:

Ï… av = (3)

Where Ï… av - apparent average flow rate, m/h;

Q'-volume flow rate, m 3 /h;

Cross-sectional area of ​​the S-test column, m 2 ;

S e , e-test measured saturation and porosity of the test ore.

In the formula, Ï… av is generally the critical liquid supply rate of heap leaching. To obtain a high concentration of metal leaching solution, is sometimes determined for the test stream Ï… av ratio is much smaller.

After Ï… av is obtained by indoor column immersion, a conventional heap leaching test can be performed with a constant Ï… av , and C p is obtained by the test, and the spray intensity Q and the total metal amount W 0 of the ore in the column are calculated.

According to formula (4)

C= e - kt (4)

Cp= (W 0 /S) (assuming t p is 0)

Or Cp= ( ) (5)

Substituting the formula (5) into the formula (3), and considering that the spray intensity Q and the volume flow rate Q' differ by one L 2 in the order,

Ï… av SS e e= Or k=Ï… av SS e e= (6)

It can be known from (6); (1) The heap leaching rate constant k can be obtained by the parameters of the indoor large column leaching test similar to the actual production conditions. (2) The heap leaching rate constant k, although not related to the chemical reaction rate constant k k and the diffusion rate constant k D , contains the factors of these two constants. Since the rate of leaching and the peak concentration of C p and C p associated metal concentration C chemical reaction rate constant and diffusion constants related substances. Relationship (3) heap leaching and heap rate constant, k e porosity and saturation S e description, diffusion and mass transfer within the pores of the material, not only by convection diffusion S e of the subject, but also on the reaction zone The diffusion of the leaching agent to the mineral surface; the diffusion of the chemical reaction product from the reaction zone to the solution body is related to the ore porosity and saturation S e . Since only most or all of the pores are filled with the solution, the dissolved metal ions and the leaching agent can undergo diffusion and mass transfer. So k is mainly controlled by S e and e. The value of the Jack Busson expression is that it illustrates or explains the essential difference between heap leaching and agitation leaching.

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