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X-Ray Transmission (XRT) sorting - How it works

The X-ray transmission technology enables materials to be recognized and separated based on their specific atomic density.

XRT simplified sorting principle

This technology makes it possible to obtain a high purity level in sorting materials irrespective of size, moisture or surface pollution level.

The COM Tertiary XRT uses an electric X-ray tube and a highly sensitive cutting-edge X-ray camera with DUOLINE® sensor technology - using two independent sensor lines with different spectral sensitivities. Data supplied by this camera is processed using TOMRA Sorting’s proprietary high speed X-ray processing unit. The system is able to identify the atomic density of the material – regardless of its thickness. 


Input material is evenly fed via a screen feeder or vibration feeder over a transition chute (both not shown) onto a conveyor belt. An electric X-ray tube creates a broad-band radiation. This radiation penetrates the material and provides spectral absorption information that is measured with an X-ray camera using DUOLINE® sensor technology. The resulting sensor information is then processed to provide a detailed “density image” of the material allowing it to be separated into high and low density fractions. If the sensor detects material to be sorted out, it commands the control unit to open the appropriate valves of the ejection module at the end of the conveyor belt. The detected materials are separated from the material flow by jets of compressed air. The sorted material is divided into two fractions in the separation chamber.