Single-Stage Hydrochloric Leaching for Bastnaesite Recovery
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Solution Overview
Problem
Current processes for extracting rare earth elements from ores, particularly bastnaesite, are inefficient, leading to low recovery rates (around 55-60%) and high chemical consumption, well below the theoretical limit of 70%, with a two-stage hydrochloric acid leach and caustic crack process being suboptimal.
Innovation Solution
A single-stage leaching process is developed, involving ultra-fine grinding of the ore to a size of 12 μm to 0.5 μm and using an acid-containing solution with a normality between 1N and 5N, typically 3N to 6N hydrochloric acid, heated to 60-100°C, to enhance the dissolution of rare earth elements, achieving greater than 80% recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-stage hydrochloric acid leach and caustic crack process is used, then the rare earth elements can be extracted from bastnaesite, but the recovery rate is low (55-60%) and chemical consumption is high
Solution Approach 1:
The patent changes key process parameters including increasing acid concentration to 4-6N HCl, raising temperature to 85-100°C, extending leach time to 4-24 hours, and reducing particle size to 12-0.5 μm. These parameter modifications transform the inefficient two-stage process into an efficient single-stage process achieving 95%+ recovery with reduced chemical consumption
Solution Approach 2:
The patent segments the ore into ultra-fine particles (12-0.5 μm) before leaching, increasing the surface area to volume ratio. This segmentation allows the acid to access and dissolve rare earth elements more effectively throughout the entire particle population, enabling complete extraction in a single stage rather than requiring multiple stages
2Productivity
If the ore is ground to ultra-fine size (12 μm to 0.5 μm), then the leaching efficiency increases, but the energy consumption for grinding increases
Solution Approach 1:
The patent modifies the particle size parameter to 12-0.5 μm, which is ultra-fine compared to conventional sizes. This parameter change dramatically increases leaching efficiency and recovery rates, making the process economically viable despite the additional grinding energy required. The ultra-fine size ensures complete acid contact with all rare earth bearing surfaces
3Productivity
If a single-stage leaching process is used with optimized parameters, then the recovery rate exceeds 95%, but the process complexity increases
Solution Approach 1:
The patent merges the traditional two-stage leach and caustic crack process into a single leaching stage. By optimizing the leach parameters (4-6N HCl, 85-100°C, 4-24 hours, ultra-fine grinding), the single stage achieves 95%+ recovery, eliminating the need for the second caustic crack stage and simplifying the overall process flow
Solution Approach 2:
The patent uses specific parameter ranges (acid normality 4-6N, temperature 85-100°C, time 4-24 hours) that create optimal conditions for complete rare earth extraction in one stage. These parameter changes ensure high recovery while maintaining process simplicity
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 single-stage leaching process achieves rare earth element recoveries exceeding 95%, significantly surpassing previous methods, while reducing the need for reagents and lowering processing costs.
Implementation Method 1
allowing the at least one rare earth element in the ore material to dissolve and leach out of the ore to create a liquor comprising the at least one rare earth element
Implementation Method 2
heating the solution up to between about 60 degrees Celsius and 100 degrees Celsius
Implementation Method 3
the solution may be agitate, or (b) may include agitating the solution
Data Source
AI summary
With the world's rapid advancement of technology, the demand and need for the materials that make up that technology has exploded. An important group of materials needed in this rapid advancement are the rare earth elements (REE) used in countless necessary applications. One source of rare earths found in the United States is bastnaesite, a rare earth bearing fluorocarbonate, mined at the Mountain Pass Mine in California. To increase production, it has been essential to optimize existing processes and create new ones to exploit current reserves. This research program was run to expand the understanding of the bastnaesite leaching system. A novel single stage hydrochloric leach system was created to optimize the rare earth extraction from bastnaesite. Typically, this process has utilized a two-stage leach system involving a high temperature hydrochloric acid leach followed by a caustic crack.