Lignin Purification via pH Adjustment and Membrane Filtration
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Solution Overview
Problem
Existing methods for lignin purification face challenges such as high viscosity, limited concentration, membrane fouling, and costly evaporation, making it difficult to achieve high-purity lignin suitable for industrial applications.
Innovation Solution
A method involving increasing the pH of a solution containing alkali lignin agglomerate colloids followed by large-pore membrane filtration and evaporation to form a lignin salt concentrate, maintaining low viscosity and preventing clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lignin solution is concentrated by evaporation, then lignin concentration increases, but energy cost and time consumption increase significantly
Solution Approach 1:
The patent changes the pH parameter of the lignin solution to induce phase separation, allowing concentration without thermal evaporation. By adjusting pH to isoelectric point, lignin precipitates while water remains, enabling separation and concentration through filtration rather than energy-intensive evaporation
Solution Approach 2:
The patent utilizes phase transition of lignin from dissolved state to precipitated state by pH adjustment. This phase change allows lignin to separate from aqueous phase, enabling concentration through solid-liquid separation methods that consume far less energy than evaporating water
2Quantity of substance
If lignin concentration is increased, then transportation and storage costs decrease, but viscosity increases making processing difficult
Solution Approach 1:
The patent maintains low viscosity during concentration by controlling pH and using phase separation rather than thermal concentration. The precipitated lignin forms a slurry with controlled water content, maintaining fluidity and processability while achieving high solid content concentration
3Quantity of substance
If direct filtration of black liquor is performed, then lignin can be separated, but membrane fouling and concentration polarization occur
Solution Approach 1:
The patent performs preliminary pH adjustment and phase separation before filtration. By precipitating lignin first and then filtering, the process avoids the membrane fouling and concentration polarization that occur when attempting to filter dissolved lignin directly, significantly improving membrane reliability and lifespan
4Quantity of substance
If lignin precipitation is performed by lowering pH, then lignin can be separated, but unwanted side reactions and co-precipitation occur
Solution Approach 1:
The patent carefully controls pH adjustment to reach the isoelectric point of lignin, where only lignin precipitates. By precisely controlling the pH parameter and using selective precipitation, the process achieves high lignin purity without co-precipitation of other components or unwanted side reactions
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
Enables high-concentration lignin salt production with reduced viscosity, suitable for industrial processes, eliminating the need for separate alkali addition and reducing transportation and storage costs, while avoiding dust explosions and maintaining solubility for thermochemical modifications.
Implementation Method 1
increasing the pH of the solution
Implementation Method 2
large-pore membrane filtration
Implementation Method 3
evaporation to form a lignin salt concentrate
Data Source
Figure 1~2
AI summary
According to an example aspect of the present invention, there is provided a method for concentrating lignin. The method comprises the steps of providing a solution comprising alkali lignin agglomerate colloids, increasing the pH of the solution, and concentrating the solution to form a lignin salt concentrate.