Glass recycling technology: using 80% recycled cullet means that approximately 12 million litres of oil and over 95 million kg of virgin raw material could be saved every year at a 300 t/day furnace.

The utilisation of recycled cullet in place of virgin raw material reduces production costs dramatically. Every percentage point of recycled glass used in the manufacture of container glass saves about 0.35 % of energy and approximately 1.1% of virgin raw material.

The quality of the

culler replacing existing raw materials needs to be of a similar standard to the material it is replacing. The impurities often found in recycled glass include CSP (ceramic, stone and porcelain), ferrous and non-ferrous metals, pyro-ceramic and an amount of other coloured glass. The quality level achieved will reflect the amount of recycled cullet used in the glass manufacturing process. If the impurity level of the culler is high, glass manufacturers will either use a low percentage of recycled cullet or accept high production losses and inclusions. Therefore production costs and losses are much higher than necessary. New separating systems ensure perfect quality for recycled cutlet. This will allow container glass manufacturers the ability to use a greater percentage of recycled cullet, minimising costs and reducing the level of inclusions.

Mixed colour glass separation

In many countries recycled container glass is collected mixed -to be able to use this material for flint and amber glass production an automatic colour separation system is required. Modern automatic colour separation plants reach colour purities similar to or better than a three colour bin collection and are more cost effective. Different colours of cullet are recognised by CCD line cameras and separated by high speed air valves and nozzles.

Off-colour separation

The colour purity after automatic mixed colour separation or 3-bin collection is normally not of the standard required by glass manufacturers. Therefore an automatic off colour separation system must to be installed, especially for flint glass, as a high colour purity is required. The new generation of CCD-line cameras reach a resolution of 0.16[mm.sup.2].

Ferrous metal separation

Ferrous metals cause metallic inclusions in container glass produced by glass manufacturers. Large ferrous metals are separated by over-belt magnets and smaller parts are removed by special neodymium drum magnets.

Non-ferrous metal separation

Non-ferrous metals also cause inclusions and can damage culler furnaces. Non ferrous metals like aluminium, lead and copper are recognised by a multi-channel RF detection coil. All non-ferrous metals and residual ferrous metals will be detected and rejected by compressed air nozzles as well.

CSP separation

Non-transparent impurities like CSP (ceramic, stones, porcelain) will also cause inclusions. CSP is detected by infrared laser cameras. The CSP detectors will even recognise and eject very small particles. To ensure highest ejection degrees a two-stage CSP separation is recommended.

Pyro-ceramic separation

Pyro-ceramics such as ceran and robax look similar to glass but are heat resistant and cause inclusions like CSP. Many different kinds of pyro-ceramic are on the market and are often disposed of together with recycled container glass. To detect and remove this type of contamination a new separator based on a special x-ray camera has been developed. The x-ray camera measures the different density of glass and will recognise pieces of pyro-ceramic which are blown out by pressed air nozzles.

* KRS Recyclinq Systems GMBH, Grafenau, Germany. Tel: +49 8552 5282. Far: +49 8552 8160. Email: krs@recyclingsystems.de