ZZS wind sifter optimizes glass recycling

A pile of broken glass has its good side too! When it comes to recycling, glass is a grateful raw material. Not only that glass has been recycled for the longest time in the circular economy, the efficiency of glass recycling also makes other industries look jealous. Glass can be recycled 100%, can be melted down any number of times and, compared to the initial production, saves a lot of energy. According to DUH, energy consumption in glass production has decreased by around 77% over the past 50 years. This thanks to modern technologies and successful glass recycling. The focus here is on its use as food packaging, i.e. use as a bottle or jar.

The recycling of glass in Germany is the model student. If collected glass packaging such as bottles or canned jars are recycled, 60% of white glass and 90% of green glass can include recycled broken glass into the new product. The remainder are sand, soda, lime, dolomite and feldspar. According to the Bundesverband Glasindustrie e. V. in Germany there are around 300,000 glass containers and in 2018 the recycling rate was 83%. Thus 83% of glass packaging consisted of recycled glass. In order to really get the most out of the throws in glass containers, wind sifter technology from TRENNSO-TECHNIK^® is used successfully. The ZZS wind sifter has an important task in the processing technology of glass recycling. It ensures efficient organic depletion and thus helps to optimize the subsequent process steps and qualities.

Glass or not glass, that's the question! In processing technology, a ZZS wind sifter is used as an organic separator to optimize the efficiency of glass recycling. Organic components such as foils, paper, dust, lightweight plastics or corks are sorted out by air separation. The dry separation process used by TRENNSO-TECHNIK^® means that pure air is used as working medium. Operated in recirculation mode, an air classifier unit is therefore an environmentally friendly system from a sustainable point of view, which consistently reflects the environmental concept of recycling.

The ZZS air sifter in action, separating glass and organic, can be seen in this video or schematically in this animation.

The material to be separated reaches the zigzag sifter via a rotary valve. Here it is distributed over the entire cross-section of the sifter channel and gets into the air flow. The classifying air generated by the blower flows through the zbox from bottom to top, flushing and separating the bulk material. At every bend in the classifier channel, the product has to cross the air flow and then hits the opposite wall of the sifter. The material with a higher density sinks downwards in the sifter channel as a result of gravity. Light goods are sucked out of the classifier duct in the upward airflow. The air speed of the blower is regulated by a frequency converter. Discharged air with the separated organic is cleaned by a cyclone separator.

Each wind sifter unit from TRENNSO-TECHNIK^® is manufactured according to customer specification requirements. In general, depending on the abrasiveness of the material to be separated, e. g. HARDOX, PU, stainless steel or ceramic are used. For glass recycling, the ZZS wind sifter is equipped with hard overlay welded exchangeable baffle plates. Ceramic is used in the pipelines and the cyclones. Systems from TRENNSO-TECHNIK^® are also available as a complete version made of stainless steel and with surface treatments that meet different requirements. Thanks to our decades of experience with a wide variety of feed products, we know the optimal system configuration for customer-specific solutions in density sorting. Tests in our in-house technical center support our process solution competence.

Wind sifter technology from TRENNSO-TECHNIK^® can be used in a variety of ways to ensure the purity of fractions for further sorting steps. Heavy parts separators are successfully used as a density separation process not only for sorting waste glass, but also for other bulk goods, other recycling or in the food sector.

Some examples for the use of ZZS z-box are:

• Processing of used glass and glass production waste
• Separation of non-ferrous metals from cable fractions
• Dust removal from slag
• Processing of shredder fractions
• Sorting household waste
• Processing of compost
• Separation of artificial turf
• Removal of impurities from waste wood
• Cleaning sand
• Cleaning tea, herbs, spices, grains, nuts

The air classifier technology is a dry separation process. The prerequisite for this is dry bulk material and a dry air flow. In the case of moisture accumulation in the air stream, the sorting results are unsatisfactory. Therefore, highly efficient separation results are achieved through automatic exhaust air control.

The use of processing technology such as the ZZS wind sifter from TRENNSO-TECHNIK^® also helps to improve the efficiency of glass recycling. The objective of obtaining the highest possible proportion of recyclable waste glass is achieved if glass fractions are successfully pre-sorted. This is attained with a high level of purity through the integration of machines and modules such as the ZZS wind sifter.