Multi-Stage LiPF6 Crystallization for Continuous Feed and Uniform Crystals
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Solution Overview
Problem
Current agitated crystallization methods for lithium hexafluorophosphate production face challenges in achieving continuous feeding and discharging, leading to low turnover efficiency and non-uniform particle sizes, with issues such as increased volatility, impurity inclusion, and mechanical corrosion.
Innovation Solution
A crystallization system comprising multiple interconnected crystallization kettles, each stage optimized for specific grain size and temperature control, allowing continuous feeding and discharging, and utilizing agitators to maintain crystal uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If agitated crystallization is used to shorten crystallization time and improve production efficiency, then productivity is improved, but volatility increases leading to raw material loss
Solution Approach 1:
The crystallization process is divided into multiple stages with different agitation intensities. During the nucleation stage, high-speed agitation is applied to promote rapid crystal formation. During the growth stage, agitation is reduced or stopped to minimize volatility and hydrogen fluoride loss while allowing crystals to grow uniformly.
2Manufacturing precision
If agitated crystallization is used to achieve uniform particles and stable quality, then manufacturing precision is improved, but mechanical seal corrosion and leakage occur
Solution Approach 1:
The agitation system uses variable speed control to adapt to different crystallization stages. High-speed agitation during nucleation ensures uniform particle formation, while reduced or intermittent agitation during growth protects mechanical seals from corrosion and extends their service life.
3Productivity
If faster crystallization speed is used to improve production efficiency, then productivity is improved, but impurity components crystallize together reducing product purity
Solution Approach 1:
The crystallization process is segmented into nucleation and growth stages. During nucleation, high-speed agitation promotes rapid crystal formation. During growth, agitation is reduced to allow selective crystallization, enabling pure lithium hexafluorophosphate to precipitate while impurities remain in the mother liquor, thus improving product purity.
4Manufacturing precision
If static crystallization is used to improve product purity through slow crystallization, then manufacturing precision is improved, but energy consumption increases and production cycle lengthens
Solution Approach 1:
The crystallization process uses periodic agitation: high-speed agitation during nucleation to promote rapid crystal formation, followed by reduced or stopped agitation during growth to maintain purity. This periodic action combines the benefits of both static and agitated crystallization, achieving high purity with reduced energy consumption and shorter production cycle.
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
Enhances production efficiency and crystal uniformity by enabling continuous operation and precise temperature control across stages, reducing aggregation and settlement, resulting in improved lithium hexafluorophosphate quality.
Implementation Method 1
further connected to the second-stage crystallization kettle through a first mother liquor delivery line configured to deliver lithium hexafluorophosphate mother liquor having a first prescribed grain size
Implementation Method 2
under the condition that the temperature of the lithium hexafluorophosphate mother liquor is controlled within a first prescribed temperature range by the mother liquor heat exchanger
Implementation Method 3
when the lithium hexafluorophosphate mother liquor supplied from the lithium hexafluorophosphate mother liquor supply source to the first-stage crystallization kettle crystallizes and grows to the first prescribed grain size
Implementation Method 4
utilizing agitators to maintain crystal uniformity
Data Source
Figure 1~2
Figure 3
AI summary
In the crystallization system of the lithium hexafluorophosphate of the present invention, a first-stage crystallization kettle is connected to a lithium hexafluorophosphate mother liquor supply source through a lithium hexafluorophosphate mother liquor supply line; further connected to the lithium hexafluorophosphate mother liquor supply source through a mother liquor heat exchange line connected with a mother liquor heat exchanger; and further connected to a second-stage crystallization kettle through a first mother liquor delivery line configured to deliver lithium hexafluorophosphate mother liquor, a second-stage crystallization kettle is connected to a third-stage crystallization kettle through a second mother liquor delivery line configured to deliver lithium hexafluorophosphate mother liquor, a third-stage crystallization kettle is connected to a fourth-stage crystallization kettle through a crystalline particle delivery line configured to deliver small crystalline particles in the third-stage crystallization kettle; and further connected to a next process device through a first discharging line, and a fourth-stage crystallization kettle is connected to a next process device through a second discharging line. The crystallization system of lithium hexafluorophosphate of the present invention enables different crystallization stages to be carried out separately in different crystallization kettles, so as to realize continuous feeding and continuous discharging in the course of crystallization.