Caliche forest
Sodium Nitrate is found in the Atacama Desert of South America in Caliche, the upper layer of a large salt deposit. .This ore is leached, and the leachate is concentrated in a series of solar ponds, from where a salt mixture containing NaNO3 with smaller amounts of KNO3 and Sodium and Magnesium Chlorides and Sulfates is harvested.
The mixing of this salt mixture with water at elevated temperatures results in a nitrate-rich solution, while a large part of the NaCl and the Sulfates remain undissolved. NaNO3 is recovered from this solution by vacuum-cooled crystallization. The remaining mother liquor is reheated and recycled as part of the leaching medium for the Caliche. A small amount of mother liquor is purged from the system, to control the concentration of soluble impurities.
Following the Leaching step, as an alternate mode of operation, Potassium Nitrate can be recovered by metathesis reaction with the addition of KCl. The metathesis step causes the precipitation of NaCl, which is separated. Nitrate and Potassium remain dissolved in the hot solution, which is fed to the vacuum cooling crystallization.
GEA Messo performed extensive test studies to define the appropriate operating conditions of this process and on the basis of this work supplied a plant for the alternative production of NaNO3 or KNO3.