TOMRA's PRO Series sorters are chute type sorters designed for the typical minerals processing environment. This simple and compact design is based on the freefall principle making it both efficient and reliable. Material is fed to the chute using a vibratory feeder. The objects accelerate while sliding down the chute before falling into the sensing zone. As they pass by the sensor an image of each individual object is captured and analyzed at rates of up to 10,000 objects per second. The sorting algorithm identifies each object as an “accept” or an “eject” and then predicts when each free-falling object will reach the valve array located just below the sensor. This valve array consists of hundreds of closely spaced, high speed pneumatic valves. When objects which the sorting algorithm has slated for ejection reach the valve array, perfectly timed bursts of compressed air deflect targeted objects over to the “ejects” bin, while objects identified by the sorting algorithm as “accepts” are allowed to continue their freefall into the accepts bin.
The simplest sorting sensors are cameras used for optical sorting, much as could be done with the human eye. But beyond this, TOMRA offers sensors capable of utilizing the complete spectrum of electromagnetic radiation including EM (radio waves), infrared, near infrared, visible light, X-ray fluorescence, X-ray transmission and radiometric (gamma rays). Using these technologies the sorter can differentiate rocks that appear identical yet have different physical traits such as electrical conductivity, heat capacitance or atomic density.
In some sorting applications a belt is preferred to a chute for presenting the objects to the sensor. TOMRA's COM sorters are used in such applications. The belt allows presentation of a non-uniform feed because the particles tend to stabilize on the belt before they are scanned by the sensor. Belt sorters can also overcome problems resulting from feeds with high surface moisture.