Lithium Extraction from Spodumene via In Situ HF Generation
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Solution Overview
Problem
Current processes for extracting lithium from lithium-bearing silicates, such as spodumene, are economically inefficient due to high energy costs associated with roasting steps and significant reagent consumption, necessitating an alternative or improved method for lithium recovery.
Innovation Solution
A process involving heating a slurry of lithium-bearing silicate with fluoride and sulphuric acid to generate hydrofluoric acid in situ, followed by washing and separating solids to produce a lithium-bearing solution, which can achieve lithium extraction rates greater than 85%, with optional steps for impurity removal and precipitation of lithium carbonate or hydroxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional acid-roasting or lime-roasting processes are used to extract lithium from spodumene, then lithium extraction efficiency is improved, but energy consumption and reagent consumption increase significantly
Solution Approach 1:
The patent changes the chemical parameters of the leaching process by using sulphuric acid instead of traditional roasting reagents, and conducts the process at lower temperatures (below 100°C) compared to conventional roasting (1030-1090°C), thereby reducing energy consumption while maintaining extraction efficiency
Solution Approach 2:
The patent extracts lithium from spodumene through direct acid leaching without the need for high-temperature roasting预处理, taking out the lithium value directly from the silicate structure using sulphuric acid and fluoride at lower temperatures
2Productivity
If conventional roasting processes are used to extract lithium from spodumene, then lithium extraction efficiency is improved, but reagent consumption increases significantly
Solution Approach 1:
The patent changes the chemical environment by introducing fluoride ions which form soluble fluorosilicate complexes, altering the leaching mechanism to require fewer reagents while achieving high extraction efficiency
Solution Approach 2:
The patent uses fluoride ions as an intermediary substance that facilitates the breakdown of the spodumene structure and formation of soluble lithium fluorosilicate complexes, enabling efficient extraction with reduced reagent consumption
3Manufacturing precision
If high-grade spodumene concentrate is produced through conventional mining and beneficiation, then lithium purity is improved, but processing complexity and cost increase
Solution Approach 1:
The patent changes the chemical parameters to achieve selective leaching where sulphuric acid and fluoride selectively dissolve lithium from spodumene while leaving other minerals intact, simplifying the processing flow while achieving high purity lithium carbonate product
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process achieves high lithium extraction efficiency with reduced energy costs and reagent consumption, allowing for the recovery of lithium values as lithium carbonate or hydroxide with minimal impurities, thereby addressing the economic inefficiencies of existing methods.
Implementation Method 1
heating a slurry of a lithium-bearing silicate, 40 to 2000 kg/t of a source of fluoride and 50 to 5000 kg/t sulphuric acid at a temperature from 70 °C up to a boiling point of the slurry
Implementation Method 2
heating a slurry of a lithium-bearing silicate, 40 to 2000 kg/t of a source of fluoride and 50 to 5000 kg/t sulphuric acid at a temperature from 70 °C up to a boiling point of the slurry; and, b) washing the slurry with water or a dilute acid solution and separating solids therefrom to produce a lithium-bearing solution
Data Source
Figure 1
AI summary
A process for recovering lithium from lithium-bearing materials, in particular lithium bearing silicates such as spodumene, is provided. The process involves the steps of mixing the lithium-bearing material with a source of fluoride, such as calcium fluoride or hydrogen fluoride, in the presence of sulphuric acid at 90 °C for ≥ 3 h to extract ≥ 80% Li. Lithium values may be recovered as >98% purity lithium carbonate by raising the pH of the pregnant liquor solution (PLS) to pH < 4 to precipitate Al and fluoride from solution, with a subsequent softening step to bulk remove excess calcium sulphate, followed by evaporation and precipitation of lithium carbonate.