Pre-Sieve Screw Conveyor Sorting for Elongated Contaminant Removal
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Solution Overview
Problem
Existing fluidized bed boilers face challenges in managing bed material loss and contamination with elongated objects, leading to sieve clogging and reduced efficiency, particularly when using ilmenite particles.
Innovation Solution
A device with a pre-sieve having elongated openings and a close proximity to the conveyor screw is used to separate elongated objects, combined with a mechanical impact device to prevent clogging, followed by sieving and magnetic separation to recover ilmenite particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard sieve is used to separate particulate ash stream, then size separation is achieved, but elongated objects like threads or wires clog the sieve openings and disrupt separation
Solution Approach 1:
The sieve structure is segmented into multiple parallel bars with gaps between them, creating elongated openings instead of traditional mesh patterns. This segmentation allows elongated objects to pass through or align with the gaps without blocking the sieve surface, while still maintaining effective size separation for particulate matter.
Solution Approach 2:
The sieve openings are extended in one dimension (length) to create elongated rectangular gaps rather than square or circular openings. This dimensional change allows elongated contaminants to pass through the sieve plane without causing clogging, while the width of the openings maintains adequate separation for particles.
2Reliability
If elongated objects are removed from the particulate stream, then sieve clogging is prevented, but additional separation stages increase device complexity
Solution Approach 1:
The pre-sieve with elongated openings serves multiple functions simultaneously: it performs size separation for particulate matter while also filtering out elongated objects like threads and wires. This multi-functionality eliminates the need for separate removal stages for elongated contaminants, simplifying the overall device structure.
Solution Approach 2:
The pre-sieve performs preliminary separation of elongated objects before the main sieve processing. By removing elongated contaminants in advance, the main sieve operates without clogging risks, and the system maintains continuous operation without requiring complex post-sieve cleaning or removal mechanisms.
3Manufacturing precision
If finer particles are allowed to pass through the pre-sieve, then separation completeness is improved, but particles accumulate on the pre-sieve surface and reduce efficiency
Solution Approach 1:
A vibration mechanism is applied to the pre-sieve to create oscillating motion that prevents fine particles from accumulating on the sieve surface. The vibration keeps the particle bed loose and allows continuous passage of finer particles through the elongated openings, maintaining high separation completeness without surface blockage.
Solution Approach 2:
The vibration mechanism operates periodically or continuously to disrupt particle accumulation on the pre-sieve surface. This periodic action ensures that fine particles are continuously cleared from the sieve surface, maintaining open elongated openings for sustained high-rate separation operation.
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 solution effectively separates elongated objects, reduces sieve clogging, and allows for efficient recirculation of ilmenite particles, enhancing boiler operation and reducing resource consumption.
Implementation Method 1
separates elongated objects from the particulate stream before it reaches the main sieve
Implementation Method 2
a pre-sieve (3) comprising elongated sieve openings formed by fingers extending towards an end portion of the pre-sieve
Implementation Method 3
the device further comprises a mechanical impact device for providing mechanical impacts to the pre-sieve
Implementation Method 4
a screw conveyor (1) for conveying the particulate stream to a separation device
Data Source
AI summary
The invention relates to a device for continuously sorting a particulate stream, comprising: a) a screw conveyor (1) for conveying the particulate stream to a separation device, b) a sieve (7) for separating the particulate stream ac cording to size, characterized in that it further comprises c) a pre-sieve (3) comprising elongated sieve openings formed by fingers extending towards an end portion of the pre-sieve with the tips of the fingers not being connected in that end portion, the pre-sieve (3) being located between the conveyor outlet and the sieve, d) wherein the pre-sieve (3) encloses part of the circumference of the conveyor screw in an axial end portion of the conveyor screw, and e) the radial distance between the conveyor screw (1) and the pre-sieve (3) is less than 10%, preferably less than 5% of the conveyor screw diameter. The pre-sieve allows to separate elongated objects like threads or wires from the particulate stream which would otherwise clog or block subsequent separation devices including the sieve.