sif trade srl

Technical description of a recycling plant

- By:

Courtesy of sif trade srl


The input material of the recycling plant comprises the “Automotive Shredder Residues (ASR)”.

The processing objectives of the different recycling stages included in the plant are described below.

Stage 1 – Size Reduction

Objective of Processing: in this process step, material shredding for the disintegration of composite materials and size reduction is carried out in a continuous process. For size reduction of the shredder light fraction the innovative “Rotorshredder” is used. Here, the maximum feed material size is 600 mm.

Input and Size Reduction of Material: a wheel loader feeds the material to a box feeder, from where it is transferred to the feeding belt of the “Rotorshredder”. In the “Rotorshredder”, composite materials are disaggregated and reduced to sizes ranging from 0 – 80 mm.

Discharge of Material: from the central discharge outlet of the “Rotorshredder” the entire shredded material is conveyed to the next process stage. In case of malfunctions, the material is also discharged from the lateral discharge slide and transported to the stockpile by means of an inclined belt conveyor.

Stage 2 – Post “Rotorshredder” Sorting

Objective of Processing: following size reduction in the “Rotorshredder”, the material is pre-sorted and classified in a continuous process in this stage. The resulting fractions are ferrous metals (large pieces) and the 0 to 2 mm, 2 to 20 mm and 20 to X mm fractions which are to be further processed separately.

Input of Material: the material reduced in size is discharged from the discharge hopper of the upstream “Rotorshredder” onto a conveyor belt and fed to the sorting stage. Most of the material is sized from 0 to 80 mm. Some pieces may measure up to 300 mm.

Sorting and Discharge of Material: after feeding the material comes the magnetic pre-sorting step. For this purpose, an overhead magnetic separator is mounted above the conveyor belt. By means of this separator large pieces of iron are separated from the material stream, which falls directly into a box or on a stockpile for temporary storage.

The remaining material stream is transported by the same belt conveyor to a vibrating trough conveyor, which feeds the material at equal shares to a screening station, where the 0-2 mm (about 50% of the total INPUT), 2-20 mm (about 20% of the total INPUT) and 20-X mm (about 30% of the total INPUT) fractions are separated. The 2-20 mm fraction is temporarily stored in a box directly underneath the screen. The 0-2 mm and the 20-X mm fractions are conveyed by belt conveyors to the subsequent processing stages.

Stage 3 – Sorting of the 20 to X mm Screen Fraction

Objective of Processing: in this process step, the final sorting of the 20 – X fraction of the pre-shredded and pre-sorted shredder light material is carried out in a continuous process. The resulting fractions are ferrous metals, non-ferrous metals, a non-conducting residual fraction (plastic, rubber, textiles,…).

Input of Material: the input material fed to the sorting stage by means of a belt conveyor is the residual fraction of the screening machine installed upstream. The material comes in sizes from 20 to 80 mm, with a minor part in the 80 – 300 mm range.

Sorting and Discharge of Material: the material stream is delivered by the belt conveyor of the screen overflow onto an inclined conveyor belt, from where it is transferred onto a drum magnetic separator with upstream vibrating conveyor. The magnetically separated ferrous fraction is fed, via a conveyor belt, to a box where it is temporarily stored until it is transported off-site. The remaining non-magnetic material goes from the drum magnet directly onto a non-ferrous metals separator (eddy current separator). There the separation into non-ferrous metals (aluminium, copper, etc.) and non-conductors (mainly plastic, rubber, textiles, etc.) takes place. The separated non-ferrous and non-conductor fractions are conveyed, via separate discharge belts, into boxes for temporary storage.

Stage 4 – Comminution/compaction of the 2 to 20 mm Fraction

Objective of Processing: to make the 2 to 20 mm material fraction sortable or improve its sortability, the last compounds in the material must be comminuted and or disaggregated, and slabby and wiry parts must be compacted as well as possible. This is done in batchwise operation using the innovative “Rotor Impact Mill”. The material involved is pre-shredded shredder light fraction of the 2 to 20 mm screen fraction.

Input of Material: the screened material is removed from the box onto a box feeder by means of a wheel loader. After pre-selection at the control cabinet of a certain processing time for the compaction, the process is started. The selected processing time is dependent on the required number of times the material passes through the mill. After the process has been started, the material is discharged from the box feeder by means of a belt drive system.

Processing Cycle: the material is conveyed to the “Rotor Impact Mill” via the downstream belt conveyor. In the mill, the compaction takes place. Following the exit from the mill, the material is returned to the box feeder via a trough chain conveyor with two discharge outlets. The trough chain conveyor discharges the material at discharge outlet 1 and the material is fed again in the rear of the box feeder. This closed cycle operation continues until the pre-selected processing time has expired.

Discharge of Material: after expiry of the processing time, discharge outlet 2, which is located before discharge outlet 1, is opened at the trough chain conveyor. This causes the material to be conveyed via chute to the next process stage. The closed cycle operation is continued until the entire system is emptied. The empty signal is produced via a time function. At the empty signal, all conveying and feeding equipment are switched off. The “Rotor Impact Mill” and the dust removal unit continue in operation. The box feeder can be newly fed from the wheel loader and the cycle can be started again.

Stage 5 – Sorting of the 2 to 20 mm Fraction

Objective of Processing: in this process step, the final sorting of the 2 to 20 mm shredder light fraction is carried out in a continuous process. The resulting three material fractions are ferrous metals, non-ferrous metals, and a light fraction (plastic, rubber, textiles, etc.).

Input of Material: the previously processed 2 to 20 mm size material is transported from a chute of the upstream trough chain conveyor to a silo for temporary storage. The material is withdrawn from the silo by means of a screw conveyor.

Sorting and Discharge of Material: at first, the material is separated into a light fraction (plastic, rubber, textiles, etc.) and a heavy fraction (metals) by means of two air separation tables connected in series.

The screw conveyor transports the material from the silo onto air separation table 1. There, the separation into light fraction 1 and heavy fraction 1 takes place. Light fraction 1 falls via a chute into a downstream drag bar feeder. Heavy fraction 1 is transported by another screw conveyor to air separation table 2 for secondary purification, i.e. the separation into light fraction 2 and heavy fraction 2. Light fraction 2 is also transferred, via a chute, to the trough chain conveyor, where it is conveyed, mixed with light fraction 1, to a loading station and temporarily stored in boxes.

Heavy fraction 2 (metals) now is transferred, via a chute, onto the magnetic separator 1 (drum magnet) where the ferrous metals are separated. The non-magnetic fraction continues directly onto the magnetic separator 2 (drum magnet) for secondary purification. Magnetic separator 2 once more separates any ferrous metals from the non-magnetic fraction. The separated ferrous and non-ferrous metals are transferred via chutes into boxes for temporary storage.

Other Highlights

The recycling plant also includes:

-          an innovative floating plant aimed to the hard plastic sorting. The floating plant only uses water and air. The water circuit is closed (in a loop) requiring approximately 300 litres per day of fresh water;

-          a central dust removal system (filter and cyclone are located outside the hall) and a control system for all plant components:

-          a system sorting Zinc, Fe-oxyd powders and other non ferrous metals out of light/heavy fractions of shredder dust.