Waste Solvent Purification via Decompression and Distillation
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Solution Overview
Problem
The existing methods for purifying waste solvents derived from supercritical drying processes are inefficient in removing carbon dioxide and ammonia, leading to increased costs and quality issues in reusing the solvents for producing silica aerogel or silica aerogel blankets, with conventional techniques either failing to remove these impurities effectively or generating harmful salts.
Innovation Solution
A method involving a decompression process to remove carbon dioxide followed by a multi-stage distillation process to purify the solvent, optimizing conditions such as temperature, pressure, and reflux ratio to maximize solvent recovery and purity, thereby minimizing solvent loss and ensuring the solvent can be reused without affecting the physical properties of the aerogel products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional purification methods (solvent addition or acid neutralization) are used to treat waste solvent, then the waste solvent can be reused, but the cost increases and impurities (ammonia or salt) are not effectively removed
Solution Approach 1:
The purification process is divided into multiple sequential stages: first decompression to remove carbon dioxide, then multi-stage distillation to remove ammonia and other volatile impurities. This segmented approach allows each stage to target specific impurities efficiently, achieving high purity without requiring expensive additional solvents or neutralization agents.
Solution Approach 2:
The process utilizes changes in physical parameters (pressure and temperature) to separate impurities from the solvent. By controlling decompression pressure and distillation temperature gradients, the method selectively removes different components based on their volatility, achieving purification without chemical reactions that would increase cost or complexity.
2Productivity
If carbon dioxide is used as supercritical fluid for drying, then the drying process is effective, but ammonium carbonate salt is generated in the waste liquid
Solution Approach 1:
The decompression step specifically targets and extracts carbon dioxide from the waste solvent by reducing pressure, causing CO2 to separate as a gas. This extraction occurs before distillation, preventing CO2 from reacting with ammonia to form ammonium carbonate salt, thereby eliminating the harmful byproduct while maintaining drying efficiency.
Solution Approach 2:
The decompression step is performed as a preliminary action before distillation to remove carbon dioxide. By eliminating CO2 beforehand, the subsequent distillation process only needs to handle ammonia and other volatile impurities, preventing the formation of ammonium carbonate salt and simplifying the overall purification process.
3Reliability
If multi-stage distillation is used to remove ammonia, then high purity solvent is achieved, but solvent loss may increase
Solution Approach 1:
Decompression is performed as a preliminary step to remove carbon dioxide before distillation. This prevents CO2 from interfering with the distillation process and reduces the complexity of vapor-liquid equilibrium, allowing for more efficient distillation with lower solvent loss while achieving the same purity level.
Solution Approach 2:
The process exploits phase transitions of different components at different stages: decompression causes CO2 to transition from dissolved state to gas phase, while distillation utilizes vaporization and condensation to separate ammonia and other volatile impurities from the solvent. These controlled phase transitions enable selective removal of impurities while minimizing solvent loss through efficient condensation and reflux.
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 approach effectively purifies the solvent to high purity, maximizing the recovery rate of the solvent and reducing production costs by minimizing solvent loss, while ensuring the aerogel products maintain their physical properties, with a recovery rate of 93% or greater and ammonia levels below 20 ppm, preventing salt formation and pH-related issues.
Implementation Method 1
decompressing a waste solvent to remove carbon dioxide contained in the waste solvent
Implementation Method 2
introducing the decompressed waste solvent into a distillation column and distilling the introduced waste solvent by a multi-stage distillation method
Implementation Method 3
distilling the introduced waste solvent by a multi-stage distillation method
Implementation Method 4
distilling the introduced waste solvent by a multi-stage distillation method
Data Source
AI summary
The present invention relates to a method for purifying a waste solvent. The present invention provides a method for purifying waster solvent by removing carbon dioxide contained in a waste solvent derived from supercritical waste liquid generated after supercritical drying by a decompression process, and removing ammonia by a multi-stage distillation process to obtain a solvent of high purity, which can be reused in producing silica aerogel or a silica aerogel blanket.