Processing of LCD screens - Waste and Recycling - Hazardous Waste

The safe extraction of valuable raw materials: robots automatically dismantle monitors containing mercury, while protecting workers’ health at the same time. According to initial projections, around three million LCD screens will be recycled in Germany in 2016. However, their backlighting system often contains mercury, which means they are classified as 'hazardous waste' in accordance with the EWC, and as 'Collection Group 3' in accordance with the Electrical and Electronic Appliance Law. They also contain valuable raw materials, such as metals and plastics, which have to be recovered in such a way, that the environment is not harmed. However, recycling specialists, Erdwich Zerkleinerungssysteme GmbH, have now developed an alternative: The company from Kaufering has developed an automatic processing system that enables mercury and other valuable raw materials to be easily extracted and recycled in an environmentally-friendly way.

Flat-screen monitors comprise up to seven layers. In addition to the valuable metal compound, indium tin oxide (ITO), they also contain mercury in their backlight components. The law requires that such devices are handled in such a way, that the exposure of nature and humans to this toxic substance are prevented. The Federal Environment Agency has laid down recovery quotas for electronic waste, which means that monitors may not be disposed of on refuse sites. Until now, the dismantling process has been too complex to be performed by machines, and has therefore been conducted manually. In particular, the dismantling of LCD screens with flat backlighting has hitherto been a complex and time-consuming process. “It is necessary to remove up to 30 screws just to separate the two halves of the housing. This dismantling procedure takes trained personnel between eight to twenty minutes, depending on the construction of the monitor and the type of background lighting,” explains Harald Erdwich, head of sales and marketing for the recycling experts.

Four-stage treatment process

Process step 1:
The individual monitors are fed onto a conveyor belt and
conveyed automatically into a closed processing chamber. In
this processing chamber, the device is pushed into the process
position.

Process step 2:
In the machine housing a jointed-arm robot equipped with
a camera system and a milling spindle is located. Using the
camera, the contours of the screen are measured.
The robot cuts open the complete structure of the LCD screen.
During the process, the fine swarf produced from this
operation is automatically extracted by a filter system.

Process step 3:
Once the screen has been cut open, it is pushed out by a pneumatic device and discharged via a belt conveyor into a closed chamber where a vacuum is maintained. Therein, the different layers of the display device are removed.

Subsequently, within the chamber, the backlighting containing
mercury (CCFL) located behind these layers can easily be
removed and disposed of in a closed waste disposal container.
During the entire process, the air in this chamber is extracted
under controlled conditions and the resulting exhaust air is
passed through a mercury filtering technology and transformed
into non-poisonous sulphide. Thus, mercury vapours are
prevented from escaping.

Process step 4:
The LCD screen freed from mercury is discharged and can
be recycled afterwards in a downstream ERDWICH plant, in
order to recover the precious raw materials such as metals and
plastics.