Caustic Digestion Process for Lithium Silicate Recovery
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Solution Overview
Problem
Current lithium recovery processes from lithium-bearing silicates, such as acid-roasting and lime-roasting, are energy-intensive and economically inefficient due to significant reagent consumption and high energy costs.
Innovation Solution
A caustic digestion process involving heating a mixture of lithium silicate with a concentrated sodium hydroxide solution, followed by dilution and removal of aluminates and silicates to produce a pregnant lithium solution, which is then evaporated to recover lithium carbonate or lithium hydroxide, reducing energy consumption and reagent usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acid-roasting or lime-roasting processes are used to extract lithium from silicates, then lithium recovery is achieved, but energy consumption and reagent consumption increase significantly
Solution Approach 1:
The patent changes the chemical parameters of the extraction process by using concentrated sodium hydroxide solution (40-80 wt%) instead of traditional acid or lime reagents. The process operates at moderate temperatures (200-350°C) under pressure, fundamentally altering the extraction chemistry from acid-based to alkali-based digestion, thereby reducing energy and reagent consumption while maintaining effective lithium recovery
Solution Approach 2:
The patent replaces the thermal-mechanical roasting process (which requires high temperatures and significant energy input) with a chemical digestion process using concentrated caustic solution. This substitution eliminates the need for high-temperature roasting while achieving comparable or superior lithium extraction efficiency
2Productivity
If conventional roasting processes are used, then lithium extraction is effective, but operating costs become uneconomic
Solution Approach 1:
The patent modifies the extraction parameters by using concentrated sodium hydroxide (40-80 wt%) at moderate temperatures (200-350°C) under pressure, achieving high lithium extraction efficiency without the excessive energy consumption of conventional roasting, thereby reducing operating costs to economically viable levels
Solution Approach 2:
The process employs cyclic operation with periodic heating, digestion, filtration, and evaporation stages. The barren solution is recycled back to the digestion step, creating a periodic but efficient operation cycle that minimizes continuous energy input while maintaining high extraction productivity
3Productivity
If high concentration caustic solution is used for digestion, then lithium extraction efficiency improves, but subsequent processing complexity increases
Solution Approach 1:
The patent recycles the barren solution (containing unreacted caustic and dissolved impurities) back to the digestion step after filtration and evaporation. This recovery and reuse of the barren solution simplifies the overall process by eliminating the need for fresh caustic preparation and reducing waste treatment complexity, while maintaining high extraction efficiency through continuous operation
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
The process achieves high lithium extraction efficiency (>85%) with lower energy costs by using caustic digestion and subsequent evaporation steps, effectively recovering lithium values from silicates like spodumene and lepidolite.
Implementation Method 1
reacting a lithium bearing mineral with a basic material of sufficient strength to dissolve the mineral
Implementation Method 2
adding lime to the diluted heated mixture in an amount sufficient to produce calcium aluminate and calcium silicate solids
Implementation Method 3
evaporating the pregnant lithium solution to increase a lithium concentration thereof
Implementation Method 4
contacting the evaporated pregnant lithium solution with carbon dioxide to produce lithium carbonate solids
Data Source
Figure 1
AI summary
The present disclosure provides a process for extracting and recovering lithium values from a lithium-bearing material, in particular from lithium-bearing silicates such as spodumene and lepidolite. The process for extracting lithium values from the lithium-bearing material includes heating a mixture of the lithium-bearing material and a caustic solution up to 350 °C. The mixture may be heated in a range of 200 °C to 300 °C in an autoclave. Alternatively, the mixture may be baked at a temperature in a range of 250 °C to 350 °C at atmospheric pressure. The heated mixture is then diluted and aluminates and silicates from the diluted heated mixture are removed to produce a pregnant lithium solution. The pregnant lithium solution may be evaporated to increase the lithium concentration thereof and lithium carbonate and/or lithium hydroxide are recovered from the evaporated pregnant lithium solution.