Electrostatic Aerosol Fiber Sorting
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Solution Overview
Problem
Current methods for measuring asbestos fibers in dusty environments are hindered by the presence of non-fibrous particles, which disrupt or mask fiber measurements, and existing devices are not effective in continuously sorting fibers from non-fibrous particles, leading to inaccurate counting and reduced selectivity.
Innovation Solution
A method involving the charging of particles by diffusion of unipolar ions and the application of an electric field between flat conductive surfaces, opposing gravity, to separate fibers from non-fibrous particles based on their trajectories, with the air flow being non-turbulent and collected on filter membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If membrane sampling or direct reading devices are used to measure fiber concentration, then fiber counting can be performed, but non-fibrous particles interfere with or obscure the measurements, reducing measurement precision
Solution Approach 1:
The device segments the aerosol stream into multiple trajectories using an electric field, separating fibers from non-fibrous particles based on their different electrophoretic mobilities. Fibers with higher aspect ratios experience different electrostatic forces compared to spherical or irregular particles, causing them to follow distinct paths through the charging region and onto the collector surface.
Solution Approach 2:
The device creates local variations in electric field strength and direction across the aerosol stream. By positioning charged plates at specific locations and adjusting their voltages, the system generates localized electrostatic forces that selectively deflect fibers while allowing non-fibrous particles to follow different trajectories, enabling spatial separation based on particle morphology.
2Measurement precision
If classic methods of collection on filter followed by post-analysis by microscopy are used, then fiber identification can be performed, but the process is time-consuming and lacks real-time capability
Solution Approach 1:
The device performs preliminary separation of fibers from non-fibrous particles before the actual counting or analysis step. By using electrostatic forces to pre-concentrate and position fibers on specific regions of the collector, the system eliminates the need for time-consuming microscopy analysis of entire filter surfaces, as only the pre-separated fiber regions need to be examined.
Solution Approach 2:
The device replaces the mechanical microscopy analysis step with an electrostatic separation mechanism. Instead of manually or automatically scanning entire filter surfaces under a microscope, the system uses electric fields to physically separate fibers from interfering particles, allowing for faster automated counting of only the separated fiber regions.
3Force
If unipolar ion diffusion charging is used to charge particles, then particles acquire electric charge, but fibers of different lengths exhibit different electrical mobility, making it difficult to separate fibers from non-fibrous particles
Solution Approach 1:
The device changes the electric field parameters (strength, direction, distribution) to compensate for the variable electrical mobility of fibers. By adjusting the voltage on charged plates and optimizing the field configuration, the system creates conditions where fibers of different lengths but similar aspect ratios experience comparable electrostatic forces, while non-fibrous particles with different charge-to-mass ratios follow different trajectories.
Solution Approach 2:
The device exploits the asymmetric shape of fibers compared to non-fibrous particles. The charged plates are positioned and configured to create electric field patterns that interact differently with asymmetric fibrous structures versus symmetric or irregular non-fibrous particles, enhancing separation based on morphological differences rather than just size or charge.
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 separates fibers from non-fibrous particles, reducing the masking effect and improving the accuracy of fiber counting, especially in dusty environments, by utilizing the difference in trajectories under electrical and gravitational forces.
Implementation Method 1
charging of the particles suspended in the aerosol by diffusion of unipolar ions
Implementation Method 2
application of an electric field between two electrically conductive plane surfaces arranged substantially horizontally; the electric field being directed such that it exerts an electrostatic force on the charged particles, opposing the force of gravity
Implementation Method 3
the electric field being directed such that it exerts an electrostatic force on the charged particles, opposing the force of gravity
Data Source
Figure 1~3
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AI summary
The invention consists of a continuous sorting method and device which emphasise the difference in trajectories that fibres having different aspect ratios and charged particles can be subject to, under the combined influence of electrical forces and gravity. According to this sorting method, these conditions utilise such a difference to recover/collect fibres separated from the non-fibrous particles present in the same initial aerosol, or to sort fibres which have different aspect ratios.