Powder Classification Preventing Sub-Micron Sticking
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Solution Overview
Problem
Conventional powder classification methods face difficulties in efficiently classifying powders with grain sizes smaller than 1 μm due to sticking issues in classifiers, which deteriorates performance and prolongs operation time.
Innovation Solution
A powder-classification method involving mixing a powder with a liquid additive, drying, loading into a fluid classifier, and classifying using a high-pressure gas heated to the flash point of the additive or lower, with a swirling air stream to prevent sticking and achieve efficient separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional classification method is used for powder with grain size smaller than 1 μm, then classification efficiency deteriorates, but operation time becomes excessively long
Solution Approach 1:
The powder is pre-mixed with liquid additive and dried before classification to prevent sticking during the actual classification process. This preliminary treatment modifies the powder surface properties to reduce adhesion to classifier walls, enabling efficient continuous operation without frequent interruptions for cleaning.
Solution Approach 2:
The classification process parameters are optimized by controlling the gas temperature to be at or above the flash point of the liquid additive (when heating is applied) or within safe ranges without heating, and by optimizing the drying conditions. These parameter changes prevent powder sticking while maintaining classification efficiency for sub-micron particles.
2Reliability
If conventional classification method is used for fine powder, then powder sticks to classifier portions, but this blocks ejection port and loading port
Solution Approach 1:
A liquid additive is introduced as an intermediary substance that is mixed with the powder and then removed through drying. This additive modifies the powder surface properties to prevent direct adhesion between powder particles and classifier surfaces, eliminating the sticking and blocking problems without interfering with the classification mechanism.
Solution Approach 2:
The patent replaces purely mechanical classification with a combined thermal-chemical-mechanical approach. By applying heat (in some embodiments) and using liquid additives, the method substitutes part of the mechanical interaction with thermal and chemical effects that reduce powder adhesion, preventing blocking of ports while maintaining classification function.
3Object-generated harmful factors
If powder is dried completely before classification, then sticking is prevented, but energy consumption increases
Solution Approach 1:
The powder is dried to a sufficient degree to prevent sticking during classification, but not necessarily to complete dryness. The drying is optimized to achieve the minimum required dryness level that prevents adhesion, avoiding excessive energy consumption while still effectively preventing powder sticking in the classifier.
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 method effectively classifies powders without sticking, even at grain sizes smaller than 1 μm, ensuring efficient and continuous operation by using diethylene glycol monomethyl ether as the liquid additive and controlling drying temperatures and times based on its flash point.
Implementation Method 1
an additive including a polar molecule is added to a powder to electrically neutralize a polarity of a powder particle so as to prevent adsorption and aggregation of particles
Implementation Method 2
prevent adsorption and aggregation of particles to form an aggregated particle having a large grain size
Implementation Method 3
the powder is classified in the fluid classifier by a swirling air stream produced in the fluid classifier
Data Source
AI summary
A powder-classification method includes a mixing step in which a powder and a liquid additive are mixed together, a drying step in which the powder mixed in the mixing step is dried, a loading step in which the powder dried in the drying step is loaded into a fluid classifier, a heating step in which a gas is heated, a supplying step in which the gas heated in the heating step is supplied to the fluid classifier, and a classifying step in which the powder is classified in the fluid classifier based on a grain size of the powder.