XRT (XRT)

XRT stands for X-ray transmission, a sensor technology that identifies material composition not by elemental fluorescence (as XRF does) but by measuring how much X-ray energy passes through a sample. Dense materials (lead, copper, tungsten) absorb more X-rays; lighter materials (aluminium, plastics, wood) absorb less. Modern XRT sensors use dual-energy detectors — measuring transmission at two different X-ray energies simultaneously — to separate the contributions of density and atomic number, producing a clean signal that distinguishes materials of similar density but different elemental composition (for example, aluminium versus magnesium).

Application in e-waste lines: XRT sensors are deployed downstream of size reduction and primary metal separation, typically to upgrade aluminium versus copper purity, detect wire bundles hidden inside crushed plastic or composite fragments, and remove residual heavy-metal contamination from base-metal product streams. A typical XRT installation is a sealed scanning tunnel above the conveyor belt, with shielding to keep ionising-radiation exposure outside the tunnel below regulatory limits. Throughput at 1-2 metres of belt width reaches 5-15 tonnes per hour with sorting accuracy of 95%+ on dense-versus-light material splits.

Where XRT wins over other technologies: XRT is the technology of choice for two specific problems. First, finding wires and metal inserts inside plastic fragments (a cable still wrapped in PVC insulation, or a copper-bearing connector embedded in PC plastic) — neither NIR nor XRF can see inside fragments, but XRT measures total density along the X-ray path and detects the hidden metal. Second, separating aluminium from heavier non-ferrous metals after eddy-current separation — eddy-current efficiency degrades for fragments below 30-40 mm, and XRT picks up the misses. Capital cost runs Rs 1.5-4 crore for a 2-metre-wide industrial XRT sorter, similar to high-end XRF or NIR systems.

Trade-offs and regulatory aspects: The active X-ray source requires Atomic Energy Regulatory Board licensing in India, periodic radiation surveys, and routine maintenance of shielding integrity — adding ongoing compliance overhead that purely optical sensors (NIR, RGB colour cameras) do not carry. The dual-energy detector also requires calibration with reference standards every 6-12 months. For these reasons, XRT is generally deployed only at the largest recycling facilities (50+ TPD or larger) where the throughput justifies the regulatory overhead.