The glass recycling process
Glass is one of the most valuable materials produced by man and its processing is extremely profitable – both in ecological and economic terms. Glass can be recycled in 100% and can be processed without damage to its quality and cleanliness. This is a quality that most common packaging materials do not have. Cullet is almost always one of the production components of most types of glass. In addition, it melts at a lower temperature, so when it is used for glass production, less energy, water and raw materials are used. This, in turn, makes glass processing extremely cost-effective in the long run, because it reduces production costs and is beneficial to the natural environment.
The origin of glass waste
Different types of glass differ in their composition and have different physical and chemical properties, which is why they are used in many areas of life. Each application requires a particular type of glass, the production of which requires different processes. During production, a lot of waste is generated, which must be disposed of by its owner (producer). Therefore, glass waste is classified in a simple way according to its place of origin into:
- clean waste – industrial waste generated in glassworks during the production process, suitable for re-melting (own glass). Such waste is generated as a result of refurbishment of glass furnaces, shutdowns of forming machines, elimination of defective products in the quality control process, internal losses.
- industrial waste – the waste generated by mass users of glass products (foreign glass) – it is generated in beverage bottling plants, breweries, chemical apparatus plants, dairy plants, lighting equipment plants, construction woodwork plants (windows, car glass, glass blocks, ornaments etc.).
- post-consumer waste – the waste generated by individual recipients in households, shops, restaurants, warehouses.
The sorting process
However, before the process of glass processing starts, it must be first sorted and cleaned. The purpose of the sorting plant is to get rid of materials that hinder the sorting process, to classify glass types and control its quality. During the preliminary stage, the waste goes to the manual segregation station.
However, it does not guarantee the right quality, therefore pre-sorted glass is subjected to the process of magnetic separation, after which it is additionally sifted using specialised sieves. The next steps are: optical sorting, which aims to increase the purity of cullet, crushing of the obtained raw material and repeated removal of non-glass elements and another optical sorting according to colour.
What happens next?
Cleaned, sorted and crushed cullet is usually taken back to the glassworks, which uses it to manufacture its glassware. It is put into the furnace with colourless cullet and special oxidants and is melted at a temperature between 900 and 1,300 degrees Celsius. In addition to glassware production, granulated glass can be used as a raw material for the production of insulating mats, foam glass, glass beads (reflective, stream and special), cement and grits for plaster.
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