High-frequency vibrating screens
Fineness of the products and system capacities varies over a huge range between different models, to satisfy individual application requirements.
For fine particle removal high G force is desirable and is achieved by higher frequency around 5000 to 6000 rpm.
Most commonly, high frequency screens are used to separate "reclaimed" asphalt pavement (RAP) into multiple sizes and fractions, which allow producers to take full advantage of the recycled materials.
After the ores get comminuted, high frequency screens are used as a classifier which selects materials size that is small enough to enter the next stage for recovery.
[4] The benefits of using high frequency screens in mineral processing can meet the requirement of fineness easily for recovery and is able to achieve a smaller size separation, reducing capacity needed for comminution stage and overall energy consumption.
A rotary sifter uses a screen which rotates in a circular motion and the finer particles are sifted through the apertures.
The rotary sifter will usually be chosen based on the nature of the substance being separated; whey, yeast bread mix, cheese powder, fertilizers.
The rotary sifter is often preferred in the non-metallurgical industry and operates in a way to achieve a dust and noise free environment.
In addition, another feature of high frequency vibrating screens are the static side plates which provide benefits such as smaller support structure, less noise, longer life, and hence less maintenance.
The high frequency (1500 – 7200 rpm) and low amplitude (1.2 – 2.0 mm) characteristics leads to the vertical-elliptical movement that rapidly transports oversized particles down the screen.
In the mineral processing industry, equipment often has to be moved to different sites depending on the jobs taken up by a company.
[5] Flux is defined as the amount of a desired component (undersize material) that has carried over the screening media from the feed per time per unit area.
Commercially perfect screening is considered to be 95% efficient [6] if the process is operated with appropriate feed concentration and size particles.
[5][6] However, the performance tends to decrease after a certain point since the slope of the deck is too high and most particles will remain on the oversized stream instead of passing through the aperture, thus, lower flux is yielded.
Based on the principle, there is an optimum frequency and amplitude of vibration [5] Transmission refers to the fraction of desired particle that passes through the apertures in the screen.
[6] The high frequency vibrating screens will often be used as a secondary screener as its purpose is to separate the finer minerals.
RDF can be used in many ways to generate electricity or even used along with traditional sources of fuel in coal power plants.
The research on high frequency screens has led to new developments in the field which enhance the operation and performance of the equipment.
These new developments include the stacking of up to 5 individual screen decks placed on top of the other and operating in parallel.
Thus, research and development is still being invested in high frequency screening equipment to improve the overall separation efficiency and also to lower costs.
It utilizes fluid hydraulic force which then can be converted into rotary power in order to generate high frequency vibration.
[17] This modification allows equipment to operate at higher frequency range, up to 8200 RPM, compared to the conventional electric vibrators.
Special Electric vibrator motors are also used to have variable frequency ranging from 3000 to 9000 rpm and have proved to be more efficient and trouble free with less maintenance.
Besides that, the induced vibration also creates an excellent condition for separating finer particles and improves the contacting probability for the materials.
Another variation that could be applied to the equipment is the "rotary tensioning system", in which it helps to provide a quicker screen media change.
[10] Therefore, multiple applications can be achieved by single equipment, as with different size of feed material can be deal by replacing screens in a very small downtime.
