Concept and calculation of washing efficiency

The washing efficiency refers to the ratio of the dissolved gold recovered by the washing operation to the dissolved gold fed to the washing operation. Since the washing process is a continuous and cyclic process, it is difficult to accurately calculate the washing rate. Therefore, whether it is countercurrent washing, or filtration washing, or the calculation of washing efficiency of combined washing, it is derived under the following assumptions:

1. The amount of ore supplied by each washing operation is equal to the amount of ore discharged.

2. Washing water, overflow of each washing and solid content in the filtrate is very small, negligible

3. The overflow (or filtrate) of the same stage of washing is the same as the gold content of the liquid in the same stage of washing (or filter cake).

4. In the washing operation, the solid gold is no longer dissolved, and the gold contained in the liquid does not precipitate.

The washing efficiency is calculated as follows:

Take the four-stage countercurrent washing process (see the left side of the figure below) as an example.

In the middle    F —— the ratio of the amount of washing water to the amount of ore supplied;

         R —— the solid-liquid ratio of the thickeners at all levels;

         L —— the liquid-solid ratio of the slurry after the leaching (concentrated machine feeding);

         K - the ratio of the gold content of the wash water to the gold content of the liquid in the first stage countercurrent washing thickener.

2. Calculation formula for washing efficiency of filtration washing

When the domestic cyanide plant adopts the filtration washing process, the first stage washing adopts a single-layer thickener to increase the concentration of the filter. The following figure is a four-stage filtration washing process. The characteristic of the process is that the washing water added by each stage of filtration washing is equal in gold content ; the filtrate filtered by each level is returned to the thickener.

In the middle    M - the ratio of filtered washing water to ore;

            P —— the ratio of water content of the filter cake to the amount of ore delivered;

Other symbols have the same meaning as before.

3. Calculation formula for washing efficiency of combined washing

In the combined washing process, the number of stages of countercurrent washing and filtration washing is different and the return point of the filtrate is different, and a plurality of combined washing processes can be formed. The figure below shows the first three stages of countercurrent washing, and the last stage is the combined washing process of filtration washing.

The meaning of the symbol in the calculation formula is the same as before.

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