The battle for waste glass

logo_smallIn Europe, we are going from huge piles of waste glass to a higher demand than available. A long time ago, manufacturers were paid absorbing waste glass but today they have to pay.

But there is still one type of glass for which the demand is in fact not existing. Indeed, since the Cathode Ray Tube (CRT) televisions are replaced by LCD (Liquid Crystal Display), the CRT´s are not remelted anymore. And as a consequence, a huge pile of glass is available for other applications.

DownloadOne function of CRT glass is to absorb the X-ray radiation, generated by the high velocity electrons bombarding the front panel with phosphor. For this important function, PbO and BaO are introduced in the glass. PbO is introducing a brown color into the screen after long use. For that reason, the PbO is replaced by SrO in the front panel of the color television CRT. This and more is well explained in the following paper about CRT´s.

The source of CRT-panel glass waste seems to be very large like found in the following reports:

  • The following  paper describes the worldwide situation and even mention cellular glass as a way to recycle CRT glass.

Foam glass is a lightweight and handy product that is especially used where heat and sound insulation is necessary [122]. Its use has increased in recent years due to it being nonflammable, waterproof, a good insulator and having a long
life. Foam glass is produced at temperatures of 700 °C and 900 °C [123]. In the production of these products, CRT glass components with a lower melting temperature can reduce the product’s melting temperature in some cases [12].
Although first applications were made entirely of pure glass, the rate of these industrial waste products being used has increased to 98% today [56]. In order to improve the mechanical properties of these products, different materials have
been used besides CRT [124]. Investigations have shown that the amounts of lead leaked through the glass foams are acceptable [125]. Foam glass is usually produced by adding a gas producing material to powdered glass and then baking it to trap the gas bubbles in the glass. These products are generally used as foaming agents, carbon-containing materials, organic compounds, and carbonates [126], [127]. Depending on the area to be used and the desired properties, other minerals can be added to the mixture and the mixture is then sintered. During sintering, the foaming agent content reacts to increase the volume and obtain the glass foam [128]. The foaming agent added to alter the properties of the produced glass foam varies depending on the grain size of the glass used and the cooking temperature [129].

  • Another paper gives the situation in the UK for CRT glass recycling and also mentions cellular glass:

Foam glass is an insulating material which can be made from post-consumer waste glass. Experience in Norway indicates that it is feasible to incorporate at least 20% CRT panel glass in foam glass. There are no known technical  barriers to using CRT glass and no adverse environmental impacts compared with using other types of waste glass. Demand for foam glass in the UK, however, is limited and there is currently no production capability. Production facilities
are being considered, but the projected demand for CRT glass in this application is low, starting at 3,000 tonnes per annum and rising to a maximum of 9,000 tonnes per annum.

  • separatorAnother  paper  mentions the recycling problems of Pb-glass from CRT and the different laws about this in Europe.
  • Further, we also found equipment to separate the panel and other parts of the CRT in the following leaflet.
  • A research paper  warns up for the eventual leach out of CRT-glass and so cellular glass based on this.
  • Last but not least, we found a another paper about the foaming of CRT-glass with SiC and TiN.

 

 

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