OLI PRESENTS AT ALTA 2018
Aqueous chemistry of lithium production
Authors: Mike Dry, Arithmetek, Inc. Canada
AJ Gerbino, OLI Systems, Inc., USA
Presentation by Mike Dry, Arithmetek, Inc. ALTA 2018
The following abstract describes the presentation that Mike Dry, president of Arithmetek, Inc. Canada will make at ALTA 2018 during the Uranium-REE-Lithium session on Friday afternoon, 25 May 2018. Mike is an OLI Consulting Partner and will represent OLI at ALTA.
Extracting lithium from ore deposits entails leaching, purifying the leach liquor and recovering lithium carbonate or hydroxide from the purified solution. Currently established technology for the extraction of lithium from brine entails evaporation, crystallization of salts, purification of the concentrated brine and recovery of lithium carbonate or hydroxide from the purified brine.
Regardless of the source, production of lithium carbonate or hydroxide uses aqueous processing, which commonly relies on chemical equilibrium. Understanding the relevant aqueous chemistry is vital for designing effective lithium technology.
Figure 1: Li2CO3 precipitation step after the liquor is separated from the initial Na2CO3 addition. The fraction of non-lithium solids is small relative to the total Li2CO3 precipitated.
This paper presents an overview of the aqueous chemistry found in lithium processing, in which both chloride and sulphate systems are used depending on the source or technical preference. The various simple and complex salts and their associated solubilities are examined via modelling of the relevant chemistry.
Potassium being a by-product of interest, the equilibrium chemistry of potassium in chloride and sulphate solutions of sodium, potassium, magnesium and calcium is covered. The recovery of lithium from brine entails the solar evaporation of large volumes of chloride brine, with various salts crystallizing as evaporation proceeds. However, it is also necessary to pump the concentrated brine, and pumping a solution saturated in any given salt can suffer from scaling that blocks lines and foul pumps. For that reason, the saturated brine is usually diluted with fresh water before being pumped. This partially undoes the evaporation, so the amount of water added is important. This paper includes a study of scaling tendencies versus dilution at the various stages of solar evaporation. Concentrated chloride brines being corrosive, this paper also presents a study of the suitability of various materials for pumping and piping these brines at the various stages of evaporation.