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PLASTIC WASHING UNITS
The meaning of “washing” is to remove dirt. But in plastic recycling it doesnt mean exactly this. For example everyone says “washing tanks”. If you want you can make an experiment. Put a piece of plastic in a cup filled of water and add also add some detergents and leave for hours or even a day. Then check out your plastic. It has exactly the same amount of dirt it was before this washing treatment. In plastic recycling washing is something more then washing.
Now, what about doing what it has been done for centuries to wash cloths: brushing and/or beating with stones or something like this, in other words making friction to remove dirt. In the 21st century the way of washing didn't change much, unless for the fact soaps are different and performing better.
The end of the story is make as much possible friction.
Do all plastic need detergents? Not at all.
If contamination is, for example, paper, sand or something that remains on the surface, detergents are useless because the process will be only to remove them from the surface while, speaking of oil, glue or other sticky dirt, matter can be different.
Sometimes, with some materials, contamination even help to make polymer to look better; for example if you leave some PPM of oil into LD-HDPE or PP you'll get a beautiful looking pellet, shining. Of course we're talking about a very little amount that should remain inside the scrap.
Most of scraps anyway need to be perfectly cleaned. It needs to perfect when a certain kind of contamination really bother being there and needs to be removed all the way.
Washing is not very complex system but we like simple and good working systems. If the material is highly contaminated you should use a pre-washing system. Mostly agro-film, PET and HDPE bottle recycling needs pre-washing.
Pre-washing will also extend the lifetime of your crusher’s blades. But will make it impossible to use dry crushers. Pre-washing systems can vary depensing on the contamination, volume and type of the material to be used.
Mixed plastics coming from garbage are highly contaminated. If you dont use pre-washing your crusher’s blades will wear out very quickly.
Film washing units are a bit different. If you will work with collected films we dont advice you a pre-washing system. But if you use agro-films you need prewash, because these films will be highly contaminated by sand, mud, stones etc. These materials will wear out your blades very easily. At this point using a low energy powered trommel will clean the 95% of the contamination by spraying water.
But if you will use silage film, where contamination is not only sand but also grass, hay, leaves and other floating contamination, it will be better to use a pre-washing machine that makes friction as well to release most of this dirt.
You wont need a pre-washing system in recycling HDPE bottles, a wet crusher and washing basins will be enough. Dont forget that more contaminated material means more machines in the line.
So, why do we wash the dirty scrap? It is obvious that to have clean, clear granules at the end of the line. What if we dont wash the contaminated plastic and dont sort them? You will never get clear granules but you will have yellowish granules which is not a good product. So washing in plastic recycling is a necessity not luxury.
USTUN İŞ MAKİNA, manufactures high quality, productive, enviroment friendly washing units, according to your demands.
Our washing units can be made of completely stainless steel or DKP sheets. Can be designed according to the recycled material.
LDPE-PP FILM WASHING LINE
It is really easy to find LDPE film material in the market. But don’t forget that just finding the material is easy. Film bales are mostly highly contaminated. Using a 50 mm hole diameter in the crushing machine is important for productivity of the line.
In the washing basins some of the dirt will be removed by sinking – floating method.
After that the material will be deeply cleaned in centrifuges. After that you need another washing basin. If this means high cost for you, you have change your material with cleaner one. Some recyclers forget that they don’t use appropriate washing units when they complain about their line doesn’t clean the material.
Actually in film washing lines thickness of the material is more important than the dirt on them. LDPE films are high in volume but low in density. If you recycle 1000 kg material of 40 micron, you will recycle 750 kg with 30 micron and 500 kg with 20 micron thick material. Also crushing and drying will be harder when the thickness reduces and this will make your machines not to work in desired capacity.
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