Scrap metal: preshred to prevent the smell of burning!

The Akros Henschel pre-shredder is the most recent tool to be installed at Rossi Recyclage’s scrap metal site in the south of France. Why invest in a pre-shredder? How do you depreciate such an investment? To these questions, the head of Rossi Recycling, not known for his retiring nature, gives a whole raft of answers. And the most interesting of all was: “Bringing this pre-shredder into service is a step towards environmental excellence on our site and that is our real task these days, the only way to stay in the race for competitiveness which recycling companies have to run, in order to continue to operate.”
Up to you to decide…

Credit :
Writing : DrRecup – le 27/02/2012

It was in 2008 that Christian Rossi made the big leap. The big leap for a scrap metal professional consists “quite simply” of installing a shredder on its site.
The shredder is the only tool that allows the value to be extracted from the metal content of composite objects and, up until now, the most effective tool for recycling cars at the end of their lives (ELVs). It is also the way of extracting value from incoming scrap iron, the overall quality of which tends to deteriorate.
All professionals dream of only working with clean demolition steel or oxygen-cutting scrap. But that type of scrap is becoming rarer and rarer and cannot satisfy the growing demand in electric steelmaking. Finally, after a long period of reflection on the future of his industry and the future of his business, the head of Rossi Recyclage chose to install a shredder on his site. Christian Rossi does nothing without enthusiasm. Now, ‘his shredder’ is one more thing which he gladly adds to the list (of things he is enthusiastic about). The proof is: every morning at six o’clock, he himself takes the controls of ‘his beast’, to check that everything is in working order. Of course, to begin with, you are enthusiastic, ecstatic to have such a machine,  producing 15 to 20 tonnes an hour of scrap. Then, gradually, you become more demanding. You realise that using a shredder is not without its inconveniences.
For Christian Rossi there were plenty, right from the start of the project: taking the environmental aspect of operating a shredder into consideration by installing a particularly effective noise reduction wall was essential in the semi-urban area where his site is. It did not stop him! In spite of the care taken in checking the scrap loaded into the shredder, from time to time, fire would still break out, causing particular inconvenience in the neighbourhood.
And then gradually, feeding the shredder became a more regular and more important activity; then once more, it was time to adapt. He also quite quickly became aware that operating a shredder involved a not inconsiderable cost, particularly where wearing parts are concerned. To solve all these problems, one solution quickly presented itself as the answer: install a pre-shredder.

Those who know him well, know that Christian Rossi has a pioneering spirit. That is how he was with the pre-shredder, like with everything else. This scrap metal professional turned to the latest pre-shredder model from Akros Henschel.
The particular feature about this pre-shredder is that it is equipped with only two shafts, while most conventional machines have three. On the Akros Henschel ZDS 220-400 machine now installed on the site, a drive shaft turns slowly, while the shredding shaft turns four times more quickly in the opposite direction.
We should emphasise that the 220-400 (with a 2200 mm wide loading opening – 400 kW of power) was the first of its type to be installed.  There are six models in the range. The machine’s structure is relatively simple: a hydraulically-opening articulated housing, two shafts, one driving the material, the other shredding it. Its processing capacity is approximately 40 tonnes an hour.
The machine is supplied from a hopper via a crane fitted with an internal vision camera, which monitors the machine to check that it is operating correctly, and a remote control to operate the pre-shredder. The material to be processed is held in contact with the drive shaft by a hydraulically-controlled flipper and a pressure limiter that prevents the risk of the shaft locking up.
The material is pre-shredded and aerated by teeth on the first shaft.
It is then grabbed by the shredding shaft which reduces the material into strips.
If the material resists and the shredding resistance exceeds the maximum engine torque, the direction of rotation of the shafts automatically reverses. A time-delay relay causes the shafts to resume their normal rotation, as soon as the blocking material is re-positioned or removed. The prepared material is extracted through the bottom of the machine where it is picked up by a conveyor, also supplied by Akros Henschel. The shafts are equipped with special teeth that prevent the material from becoming compacted, which is obviously not the object of the exercise. The teeth are coated with an anti-wear loading. Before the arrival of hydraulic opening of the housing, the maintenance of pre-shredders was a delicate, long-winded and sometimes hazardous operation.
The hydraulic opening of the housing on the ZDS simplifies matters a great deal. It allows the shafts to be extracted easily, in order to re-load them outside the pre-shredder under optimum safety conditions for the operator doing the work. It also simplifies the changing of the wear plates.
“The pre-shredder’s down-time is reduced to a minimum, thanks to a set of shafts being pre-supplied, allowing the teeth to be re-loaded while work continues”, says Jérémie Darcissac.
On Christian Rossi’s site the pre-shredder was installed on a steel chassis, thus requiring a minimum of civil engineering and simplifying any future move in the event of a reorganisation of the site. The question arises of the integration of the pre-shredder into the continuity of the shredding chain.
Christian Rossi finally opted for a load break between the pre-shredder and the shredder, so as to more easily handle any shortcoming in a link in the chain.  Once the machine was installed, that was not the end of it. It is then necessary to go in search of the optimum production level from the pre-shredder/shredder combination, constantly analysing its performance, i.e. looking for the best compromise of granule size of the product exiting the pre-shredder.
Gritting his teeth, Christian Rossi evidently took a lot of trouble to calibrate the machine and estimates that it is now running at its optimum setting. Throughout the test period, Rossi Recyclage’s boss also derived a certain pleasure from playing the role of tester.  And Jérémie Darcissac, Akros Henschel sales manager for France, emphasises the quality of the cooperation during the experimental phase between manufacturer and customer.

When you think of “pre-shredding”, you usually think of “increasing the shredder’s production” and “improving safety”. It is true that, from these two points of view, installing a pre-shredder brings quite satisfactory results.
The “hollow body” remains the shredder’s main enemy and despite all the care taken with the input material, explosions associated with the presence of hollow bodies still occur frequently. No risk, once it has passed through a pre-shredder: LPG tanks, which are the source of so many incidents, and other hollow bodies are opened to the air, removing the risk of explosion. By limiting explosions, the fire risk is diminished and, even if the fire which seriously damaged the site some time ago, was not caused by an explosion in the shredder, Christian Rossi does not want to go through the experience again. Any solution that reduces the risk is a good one to adopt.
A pre-shredder  does not pay for itself just by eradicating a number of risks. It is also a source of savings in “hard cash” terms. Hammers and wearing parts are put under less strain when they work on “pre-chopped” material. “What wears out a shredder,” Christian Rossi emphasises, “are load peaks. These are practically done away with, you make electricity savings and, at the end of the day, the consumption of the pre-shredder/shredder combination is no greater than that of the shredder alone when it was operating without preparation of the material. With shredding being done under optimum conditions, you get a better quality of scrap in an environment  which has improved from a noise point of view. A considerable advantage,” according to Christian Rossi, “is that the pre-shredder also allows you to fully control the quality of the input material and, where necessary, to apply classifications that cannot be disputed. Avoiding such discussions also ends up saving you time”.

The site is 50% supplied with ELVs, a certain proportion of which are always delivered pre-crushed. For these pre-crushed vehicles, Christian Rossi estimates that it will indeed be difficult to achieve the 95% recovery rates required by regulations.
As to the remaining 50%, this is mainly scrap iron for shredding coming from public tips.
Concerning ELVs and pre-crushed vehicles, one can easily imagine the benefit of a pre-shredder and its work to “de-densify” the material to be processed.  But for Christian Rossi, the pre-shredder is also a good preparation tool for bulky scrap iron that is not of the right density, by preparing a material that can be picked up more easily by a shredder’s drive rollers.
After a few months of experimentation, he now reckons that “it would no longer be possible to sensibly operate a shredder at a reasonable power without the use of a pre-shredder.”

On Christian Rossi’s site, changes are in full swing. At the same time as he was starting to use the pre-shredder, he was finalising a de-pollution unit for end-of-life vehicles. He was preparing the installation of a conveyor at the exit from the press. Two electric cranes were being installed, still with a view to giving consideration to the environment, which had the practical result of ISO 14001 certification.
The arrival of a QSE manager (Quality, Safety, Environment) should provide rapid access to ISO 9001. That is not all on the certification side, since this company in Monteux is among the first in France achieve “Cessation of waste status” approval.
If we are surprised by this commitment, Christian Rossi retorts that, ”being only small, you obviously feel vulnerable under the growing volume of regulations.  You are always being driven to do ‘better and better’ and you end up by noticing you’re your performance has improved. And that’s a good thing because you are  sometimes a little afraid of the permanent changes in the texts that surround our businesses. But we engage in constructive relations with DREAL (regulators), since their representatives have clearly understood that we are definitely committed to a progressive approach.”
If, with the installation of the pre-shredder on his site, a certain number of questions have been resolved on the preparation of scrap before it goes into the shredder, it is now what to do about post-shredding which pre-occupies Christian Rossi.
To comply with the environmental requirements that now surround end-of-life vehicles, being content to extract scrap iron and non-ferrous metals is no longer sufficient. For this company, 2012 will be a year of making use of the residues from vehicle scrappage.
Christian Rossi has a head full of projects and, when some of them come to fruition, we will continue to marvel at the dynamism of this small company.


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