BHS Sonthofen ASR plant on the job in Finland

An auto shredder residue (ASR) recycling plant recently installed for a customer in Finland by the company for which I work, Germany-based BHS-Sonthofen, recovers fine nonferrous fractions and separates them in a single processing stage.

Finnish scrap company Kajaanin Romu Oy began operating the first BHS-Sonthofen plant for recycling ASR in 2016. At the plant, nonferrous metals are separated into light and heavy fractions during the same processing stage. This allows plant operators to economically produce fractions that can be sold profitably. Moreover, the plant significantly reduces the costs of disposing of material at landfills.

Kajaanin Romu operates one of Finland’s most cutting-edge plants for recycling scrap in the town of Kajaani, located approximately 500 kilometres (310 miles) northeast of Helsinki. The company commissioned a BHS-Sonthofen plant for processing ASR metal fine fractions with a particle size between 0 and 30 millimeters (1.2 inches).

METAL IN THE MIX

Experience has shown that heavy nonferrous fractions of material left over after shredding and processing large automotive, electrical or scrap components still hold value. A metric ton can contain up to 20 grams (0.7 ounces) of gold and up to 200 to 300 grams (7 to 10.5 ounces) of silver, as well as platinum and other precious and nonferrous metals.

The main component of previous plants designed by BHS-Sonthofen to handle ASR is the rotor impact mill type RPMV, made exclusively by BHS-Sonthofen. The RPMV features horseshoe-shaped hammers and the inside features a rotating plate to which the impact elements are attached.

The material to be processed is fed into the machine from above via a central inlet pipe. When it impacts with the rotor, the material is accelerated toward the outside through centrifugal force. There, the hammers hit it and throw it against the outer wall. Upon impact, the material to be processed breaks.

After the material rebounds from the anvil ring, it comes into contact with the hammers again, which further crush it, shape it into balls and throw it back against the anvil ring. This is repeated until the material leaves the rotor through the gap between the rotor and the anvil ring and falls through the two outlet shafts.

Since the gap between the horseshoe-shaped hammers and the anvil ring is adjustable and the circumferential speed of the rotor is variable, the BHS rotor impact mill can be used flexibly for the widest variety of tasks.

The hammers can be manually removed, installed and adjusted without tools or lifting gear. The virtually constant gap between the anvil and the hammers ensures the consistent quality of the end products throughout the entire service life of the wear parts. The entire inlet cover can be rotated for optimum accessibility, which greatly simplifies maintenance of the machine.

Operators of ASR plants from BHS-Sonthofen say they can earn about €3,000 ($3,200) more per tonne when selling substances such as heavy fractions of nonferrous metals, and that the plants pay for themselves within nine to 12 months.

BHS-Sonthofen has taken the technology further by adding another stage to the plant: Metals now undergo secondary cleaning in the plant, and nonferrous metals are separated into heavy and light batches in a single processing stage. As such, BHS-Sonthofen has made previously required additional process stages obsolete.

The first of these new types of plants with increased fine fraction processing has been in operation at Kajaanin Romu since the spring of 2016. The Finnish recycling company learned about the new machine at a German trade show in June 2014 and placed an order for it three months later. The plant went into test operation in the fall of 2015.

BHS-Sonthofen delivered the turnkey plant complete with components required for all tasks, from filling to loading and dust removal.

The plant is fed fine fractions with a particle size of under 30 millimetres (1.2 inches) from the shredder, thus processing fractions that could not be used prior to introducing this plant. In the first part of the process, the feed material is crushed and the light materials are separated. In the second stage, the remaining material is screened and separated into different fractions.

SHREDDING AND SEPARATING

The rotor impact mill of type RPMV 1513 is the centerpiece of the shredding stage: It crushes the remaining material and separates it. In doing so, it works selectively, finely crushing brittle materials such as mineral substances, glass and castings and separating composites. Elastic materials such as rubber, on the other hand, remain intact.

The metals can be reclaimed since the rotor impact mill shapes the ductile metals, meaning the ones which can be physically formed, into balls. This is necessary for nonferrous metals to be cleanly separated from other materials in the downstream process. The material, which is originally often long and flat, must be compact and as round as possible to enable separation of the nonferrous metal pieces in subsequent processing stages.

Each loaded batch passes through the mill several times. Before each step, light material and dust are separated out and discharged from the mill. The rotor speed and the number of cycles can be altered to adjust the crushing behavior of the machine.

After the last cycle in the rotor impact mill, the material passes through a hopper into a screening machine that separates it into three fractions: 0 to 3 millimetres (less than one-eighth of an inch), 3 to 6 millimetres (between one-eighth and one-quarter inch), and 6 to 12 millimetres (between one-quarter and one-half inch). Each of these is separated into heavy and light through density separation. The heavy material that contains the metallic components is separated into magnetic and non-magnetic metallic fractions using magnetic separators.

As a new feature in this processing stage, nonferrous metals are then immediately separated into heavy (e.g. copper, gold and silver) and light (e.g. aluminium) fractions. This ensures all metals are cleanly separated into individual fractions during a single processing stage without requiring the material to be reintroduced to a previous process within the plant. Moreover, the plant also generates a light fraction that primarily consists of plastic pieces. This fraction is suitable for thermal utilization and does not need to be disposed of at landfills.

Two hoppers – one in the process before the rotor impact mill and one before the separation – split the individual batches. With this setup, BHS-Sonthofen has achieved virtually continuous operation. While the rotor impact mill is working, another batch is prepared in the mill cycle and a third one is screened and sorted.

THE END RESULT

Test operation was completed at the end of 2015, and the plant went into production in the spring of 2016. It has been achieving a throughput of around 10 tonnes per hour ever since. At the end of the process, all the fractions lie cleanly separated in silos. Alongside the previously mentioned volumes of precious metals such as gold, silver and platinum, the nonferrous metal fraction also includes large quantities of aluminium, copper and brass, which also is marketable. The proportion of salable nonferrous metals amounts to about 5-to-7% of the delivered volume.

Moreover, BHS-Sonthofen’s ASR plants not only increase revenue from selling metals, they also save operators from having to pay additional landfill costs. The rotor impact mill’s low-wear design incurs far fewer operating costs than other systems do.

Operators also financially benefit from the fact that the entire process is largely automated. Only one employee is required to control and monitor the entire plant. Another employee spends about half of his or her working hours on the material logistics.

BHS-Sonthofen’s ASR plants are suitable for processing fine fractions from automotive shredders as well as waste incineration plant slag and electronics scrap. This means that recycling companies can adapt their product portfolio to meet increasing requirements. The higher the proportion of electronic components and platinum in vehicles and electronic devices, the greater the volume of valuable substances that can be brought back into the materials recovery process.

The author is head of planning for crushing and recycling technology at BHS-Sonthofen GmbH, based in Sonthofen, Germany.