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Sampling of salts in pond harvesting stage

Faena: SQM Salar

Deadline 23/11/2022

Closing Time 4:00 pm

In the stage of harvesting precipitated salts from evaporation ponds, ridges are generated by machinery (see Annex I). These ridges of variable height (1 to 3 m) allow the brine, which is impregnated in the solid salt, to drain by gravity. After 30 days, the ridges are sampled and transported by truck to the storage area.

Integral technological solutions are sought that consider the design, methodology and also the necessary equipment to obtain salt samples, in order to ensure that representative samples of the impregnation in the ridges of the harvesting process are obtained.

  • With respect to the methodology, it should define the place where the sample is to be obtained (cordon, loader bucket, truck hopper, stockpile or other), the sampling grid (spatial density), sample size, sample handling from collection of the increment to the point of characterization, number of increments to generate a representative sample, and sampling frequency.
  • It should not incorporate substances or additives that alter the composition of the sample.
  • Minimal involvement of personnel during sample collection. The equipment to propose must:
  • Ensure the application of the proposed methodology.
  • Be compatible with the physical and chemical characteristics of the harvesting salt (% of impregnation, granulometry, among others).
  • Have heavy duty constructability characteristics to operate in extreme climatic and operational conditions (corrosion, abrasion, temperature, irregular and limited terrain to maneuver, among others).
  • Consider the minimum operational interference in the harvesting stage, being compatible with safety standards.
  • ┬áSolutions that alter the quality of the sample.
  • Solutions not compatible with the harvesting process.

The sampling procedure is performed by an operator using a rotary hammer to extract 3 to 6 increments to form a representative sample, on one side of the window of the ridge. The rotary hammer reaches a depth of 15 to 20 cm. Once the samples are generated, they are sent to the laboratory to determine their physical and chemical characteristics (see Annex I).

The current procedure to determine impregnation presents variations with respect to the expected values for this parameter, as well as bias in obtaining increments that generate representative samples to determine impregnation in the ridges, which could affect the estimation of impregnation in salts and therefore the reconciliation of the mass balances.

Each time harvest salt sampling is performed

By means of the methodology described in Annex I.

Technologies such as hand probes, motorized auger, sonic and diamond drilling have been tried, however, none of them prevented the loss of impregnation during sampling.