Use effect of anti-scaling agent in heap leaching

Regarding the use of anti-fouling agents, the American Mining Engineering Association organized a symposium on anti-scaling in heap leaching in 1983. The meeting expressed opinions on the effects of some practical anti-scaling agents. :

Phosphate compounds such as sodium hexametaphosphate, sodium tripolyphosphate, organic phosphate and the like, Carlin gold mine effect can be used, but most participants felt that the scale preventing effect is not satisfactory phosphate compound, such as Oti Gold mines such as Northumberland believe that phosphate compounds can only slow down scaling or soften scales, and at low temperatures, polyphosphate feedstocks are difficult because of their high viscosity and inconvenient handling.

Polyacrylate is a kind of strong anionic dispersant, its anti-fouling effect is very good, the dosage is generally (1 ~ 2) × 10 ^-5 , Alikatrich and the two gold mines mentioned above The effect of using phosphate first is not ideal, and then changed to polyacrylate. It is considered that the anti-fouling effect of polyacrylate is very good.

Malaic anhydride is believed to be the best anti-fouling effect. Dosage (0.5 ~ 1) × 10 ^-5 , Zoeterman mine. When the content of Ca ^{2 +} and CO ₃ ^{2 -} in the leachate is not high, the antifouling agent can basically control the scaling. When the content of Ca ^{2 +} and CO ₃ ^{2 - is} slightly higher, the generated scale does not form a hard. Shell, but mud.

It has been reported that magnetic fields are used in boiler water treatment to prevent scaling of calcium carbonate in water. In a meeting it was proposed to use magnetized water to prevent scaling in heap leaching, but participants felt that doing this work was unsuccessful. Perhaps due to insufficient research work or due to the particularity of the heap leaching project, there have been no reports of successful examples in this regard.

Domestic research on scaling and anti-fouling in gold ore heap leaching and alkaline in situ leaching of uranium has also been conducted. Chen Mingyang and others compared the effects of several anti-fouling agents. They believed that the anti-scaling effect depends on the concentration of Ca ^{2 +} , CO ₃ ^{2 -} in the medium, the amount of anti-scaling agent, time and other comprehensive factors. 1 combined their findings.

Table 1 Comprehensive test results of several anti-fouling agents

As can be seen from Table 1:

First, adding a small amount of anti-fouling agent, inhibiting calcium carbonate scale;

2. When the calcium concentration is fixed and the carbonate ion concentration of the medium is changed, the amount of calcium carbonate precipitation also changes;

3. When the type and amount of anti-fouling agent are different, the anti-fouling effect is different;

4. Even if anti-fouling agent is added, the precipitation of calcium carbonate will gradually form in the solution over time, that is, the anti-fouling agent can only delay the formation of scale;

5. Comparing the performance of the precipitated calcium carbonate precipitate, it is known that the calcium carbonate precipitate without the anti-fouling agent is dense and hard, has strong adhesion, and will form a hard shell. The calcium carbonate precipitate formed after the addition of the anti-fouling agent is a soft mud-like substance, indicating that the addition of the anti-fouling agent changes the crystal form of the calcium carbonate.

Jin Wenlong et al. studied the scaling of uranium in situ by alkali leaching. Table 2 shows the results of analysis of the chemical components of the scale.

Table 2 Analysis results of chemical components of scale (%)

It can be seen from Table 2 that the alkali leaching of the scale in the uranium is basically calcium carbonate, calcium sulfate, and less silicate compounds. Sodium hexametaphosphate is used as an anti-scaling agent, and the anti-scaling effect is related to the concentration of calcium ions and the amount of anti-fouling agent. Their experiments also showed that with the increase of time, the calcium carbonate in the medium will gradually precipitate.

The results of tests and production practices at home and abroad prove that the anti-scaling agent can inhibit or alleviate the growth rate of scale and change the crystal form of scale; however, if the scale-forming component contained in the solution exceeds its solubility product, even if it is added The fouling agent will gradually precipitate out, but the rate of precipitation slows down and the morphology of the crystal changes. Anti-fouling agents prevent the precipitation of substances such as calcium carbonate and are not permanent. The previous emphasis on the correct choice of anti-fouling agent addition point is also due to this consideration. The precipitation is to be formed sooner or later, the key is where the precipitation occurs to ensure the smooth operation of the operation.

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