Crossflow Membrane Filtration for Oxidic Nanoparticle Fractionation

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Solution Overview

Problem

Current membrane filtration methods for fractionating oxidic nanoparticles are limited by the formation of cake layers on the membrane, which prevents effective classification and are not scalable for industrial use, especially when dealing with dispersions containing both nanoparticles and coarser particles.

Innovation Solution

The method employs cross rotation filtration with driven rotating parts to decouple the flow over the membrane from the feed, achieving high cross-flow velocities and preventing cake layer formation, allowing for the fractionation of oxidic nanoparticles on an industrial scale by using membranes with pore diameters up to 10 μm and rotating internals to generate shearing forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If dead-end filtration is used to separate particles from suspensions, then filtration can be performed, but cake layer formation occurs which prevents effective classification and makes the method unsuitable for industrial scale

Engineering Contradiction:

Improveindustrial scale fractionationVSAvoidcake layer formation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies cross-flow filtration where the filtration medium is set in motion relative to the particle dispersion, creating dynamic flow conditions that prevent static cake layer formation. The driven rotating parts generate continuous shear forces that keep particles suspended and prevent deposition on the membrane surface, enabling continuous operation at industrial scale without the cake layer problem inherent in static dead-end filtration.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent utilizes hydraulic principles by employing cross-flow filtration where fluid dynamics play a central role. The driven rotating parts create high cross-flow velocities that generate shear forces sufficient to prevent particle deposition. The hydraulic flow regime is carefully controlled to maintain particles in suspension while allowing selective passage through the membrane, solving the cake layer formation problem.

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Manufacturing precision

If membrane filtration is used to fractionate nanoparticles, then separation can be achieved, but the specific interaction between particle and membrane influences separation outcome and limits effectiveness

Engineering Contradiction:

Improveparticle classification precisionVSAvoidseparation effectiveness across different particle types

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the flow regime parameter from static to dynamic by implementing cross-flow filtration with driven rotating parts. This parameter change transforms the interaction between particles and membrane from one dominated by adhesion and cake formation to one dominated by hydrodynamic shear forces. The continuous motion and high cross-flow velocities modify the separation mechanism to be less sensitive to specific particle-membrane interactions, improving both precision and versatility.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If sedimentation or centrifugation is used to separate coarser particles from nanoparticle dispersions, then separation can be achieved, but extreme surface-area and time requirements make these methods impractical

Engineering Contradiction:

Improveseparation efficiencyVSAvoidseparation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent replaces the gravitational field-based separation mechanisms of sedimentation and centrifugation with a membrane-based filtration system driven by mechanical rotation. Instead of relying on gravity or centrifugal forces that require extreme surface areas and long times, the system uses driven rotating parts to generate high cross-flow velocities and shear forces that enable rapid separation. This mechanical substitution dramatically reduces both the time and surface area requirements while maintaining high separation efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables the prevention of cake layer formation and allows for the effective fractionation of oxidic nanoparticles, achieving a narrow size distribution and preventing the loss of target particles, making it suitable for industrial-scale applications.

Implementation Method 1

rotating internals to generate shearing forces

Methodology Applied

Scientific EffectShear stress: Shear Stress

Implementation Method 2

achieving high cross-flow velocities

Methodology Applied

Scientific EffectCross-flow: Couette Flow

Implementation Method 3

membrane crossflow filtration step, the dispersion being caused to flow over the membrane

Methodology Applied

Scientific EffectPhysical filtration: Filter (physical)

Data Source

PatentUS8764992B2Method of fractionating oxidic nanoparticles by crossflow membrane filtration

Publication Date: 2014.07.01 EVONIK OPERATIONS GMBH

AI summary

A method of fractionating a dispersion of oxidic nanoparticles wherein at least one step of the method is a membrane crossflow filtration step, the flow of the dispersion over the membrane being brought about by means of driven rotating parts; and dispersions of oxidic nanoparticles that are obtainable by the method.