The primary shredder sets the pace for all subsequent processes and must continuously produce homogenous output from input material that is partially mixed with foreign objects. The resulting uniform and sortable material usually has a grain size of between 200 and 400 mm. Our JUPITER, the industry’s number-one permanently operational shredder is designed for continuous operation of up to 24 hours a day.
Since the material is already ‘clean’, a secondary shredder or granulator – usually a high-speed rotor shredding system – is used to shred the material to an output size of 15–30 mm. Our high-speed KOMET series with its shear cutters and always precise cut facilitates the highest output rates combined with a maximum uptime of up to 24 hours a day.
The shredder must be particularly sturdy and resistant to foreign objects in order to shred the broad spectrum of partially bulky input materials. The aim is cost-friendly processing with the lowest possible €/ton ratio for the operator and continuously steady output between 50 and 100 mm – that is ready to be incinerated in cement kilns/calciners or as fuel for fluidised bed combustion.
The shredder must be particularly sturdy and resistant to foreign objects in order to shred the broad spectrum of partially bulky input materials. The aim is cost-friendly processing with the lowest possible €/ton ratio for the operator and continuously steady output between 50 and 100 mm – that is ready to be incinerated in cement kilns/calciners or as fuel for fluidised bed combustion..
The process starts with untreated waste from households, commerce and industries being fed – often via wheel loaders, diggers or dosing conveyors – into the primary shredder. The aim is to obtain homogeneous, sortable material ready for the next step in the process.
In the second step, a magnet fitted above the conveyor belt is used to securely extract ferromagnetic parts such as scrap iron and other ferrous scrap metal. Ferrous scrap metal in premium solid recovered fuels is said to spoil its quality. Once separated, it can be recycled in line with the circular economy concept.
In the third step, the pre-shredded material – now free from any ferrous metals – arrives in a continuous stream of material. The fine grains that are undesirable in SRF but that are often found in the input material are screened at this point. The screening technology can be selected and matched to your exact requirements. Common equipment includes drum screens, strainers, vibrating screens or disc screens. Depending on your requirements, it is possible to extract different fractions in this process stage such as fines of <10 mm and oversized fractions to obtain high-quality, medium-particle solid recovered fuel.
Heavy fractions might cause increased wear or stand still in the secondary shredding process, that is the reason why such fractions are sorted out. The material stream is fed continuously into a separator where it is hit with an air current while it is in free fall. In this way, light materials are transported by air to the conveyor belt, whereas heavy materials fall to the ground to be discharged. Thanks to the circulating air, hardly any fresh air is needed.
In the final stage of the process, the material is shredded a second time in a process called fine shredding or granulation. The material that is now free from foreign matter, heavy fractions and ferrous metal and fed into one or more secondary shredders depending on the system’s throughput capacity. The output is then known as the final product or premium solid recovered fuel (SRF). Systems typically generate up to 40 tons of final SRF per hour – and that 24 hours a day.
Shredding of municipal, commercial and industrial waste for incineration with energy recovery in the main burner
Solid Recovered Fuels (SRF) are mostly used in the main burners of rotary kilns and are categorised as solid alternative fuels. The main burner needs fuels that are easily flammable and burn in a way that high material temperatures can be achieved in the kiln’s sintering zone; these are necessary to form the desired clinker minerals (approx. 1,450 °C). For that to happen, the flame has to reach an operation temperature of approx. 2,000 °C. It is therefore vital that the SRF is composed of particles that have been cut perfectly.
The SRF must be free of foreign matter (e.g. metals, stones or glass) which might cause feeding problems or issues with the clinker quality. With perfectly coordinated processes, Linder high-end primary and secondary shredders, and double extraction of foreign matter, extremely reliable and robust SRF processing with minimum maintenance is guaranteed. Featuring some of the highest throughput rates on the market and ideal output quality, Lindner’s machines also boast surprisingly low energy consumption.
Kiln main burner fuel characteristics
|Grain size||<35mm, non-3-dimensional|
|Calorific value||>4,500 kcal/kg|
|Density||>60 kg/m3 <200 kg/m3|