Chapter 1. Spiral
A spiral concentrator uses gravity to separate particles of different densities. It is used globally in the mineral processing industry. It is one of the most effective, low-cost devices for the gravity beneficiation of ores. Manufactured from lightweight, corrosion and abrasion resistant materials, spirals require a minimum of maintenance and upkeep. Consists of an open trough that twists downward in helix configuration about a central axis. Particles fed to the top of the concentrator are separtated radially on the basis of density and size as the slurry gravitates downward.
Spirals are made of fiberglass onto which smooth urethane surface is molded to form a trough in the shape of a spiral as the name suggests. Between individual spiral types, the profile of the trough and the pitch as well as the diameter and height and number of turns can vary according to duty. Feed slurry is introduced at the top and is subjected to a combination of gravitational and centrifugal forces imparted by its motion down the spiral. This causes high SG minerals to move towards the centre of the trough and water and low SG minerals towards the outside. The segregated slurry discharging from the spiral at the bottom can thus be separated by cutters into high SG (concentrate) and low SG (tailings) together with intermediate SG (middling).
Single Start Spiral
§1.2 Applications of Spirals
Spiral concentrators have, over numerous years, found many varied applications in mineral processing, but perhaps their most extensive usage has been in the treatment of heavy mineral sand deposits, such as those carrying ilmenite, rutile, zircon, and monazite, and in recent years in the recovery of fine coal.
Spirals are commonly used to separate sand sized particles with moderate SG differential in the range -2mm +75um, although varieties exist that can separate reasonably efficiently down to 38um. Below this size range efficiency falls off rapidly, and enhanced fine gravity separators are generally required.
Applications for spiral separators
• Mineral Sands
• Iron ore
• Silica Sands
➢ Modular feedbox
➢ Product box
Modular feedbox – The feed point to a spiral separator is an area where the feed slurry is normally relatively fast flowing. The duty of the feedbox is to dissipate some of the energy in the feed slurry and present the feed to the top of the separation trough in a homogenous and quiescent slurry distributed across the width of the spiral trough. The modular feed box system achieves this objective with replaceable componentry that can withstand a high impact abrasion.
Splitters- Each spiral start has six concentrate collection splitters which direct the concentrate into the inboard collection trough. These splitter mechanisms are designed for easy adjustment and repeatable positioning (using a graduated scale). They have a positive splitter-to-spiral seal and are able to handle a high volume of concentrate. All splitter handle indicators are readily visible so that the operator s can see and adjust large numbers of handles accurately and quickly.
The splitter is used to direct the
particles to their respective discharge
At the end of the spiral there is a
Splitter and discharge part
Repulpers – The installation of repulpers on spiral troughs improves the separation efficiency of spiral separators. The function of repulpers is to capture and divert a portion of water from the high velocity tailing stream and introduce it to the relatively sluggish middling stream in order fluidise the particle bed and re-initiate separation mechanisms .
Repulper to Direct water from Outer Spiral Wall To concentrate collection area
Product Box- The collection and laundering...
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