Sorting Methods

The different sorting methods for plastic scraps

 

Technology in this field did big steps ahead lately. Of course we're talking about automatic sorting systems. NIR detectors can sort all kind of different plastics, together with colors etc.

Easy, isn't it ?  OK, lets go to see the back face of the medal. Let's divide also this page into different chapters:

 Plastics coming from garbage selection:

 For this purpose we are keen to approve this way of doing because the NIR detectors can handle a pretty good quantity of scrap material and because separation is, in practice, something like 92-95% the machine pays for itself in not a long time.

Please note we said 95% top as separation efficiency. (actually like manufacturers do)

So, if after this you go into a washing and separation process, you' will remove the rest of contamination pretty easily with some exceptions.

The HDPE bottles stream will have some (little) film (LDPE), some PET and PVC bottles and practically nothing else, separation in any washing line will easy and the product at the only HDPE and the 2% LDPE that, may be remains inside, doesn't bother at all.

Almost the same applies to PET bottles that require further sorting anyway. (we'll talk about this later)

As far as LDPE film concern here the true:

Together with film there will be HDPE bottles, and this not big deal, some PET bottles as, and this can be handle quite easily as well, some PS trays not easy to remove by sink-float tanks but, the most difficult and messy materials will be sponges, all kind of foamed materials and last but not least, cleaning pads, a piece of cloth, some cotton fabric and craps like these.

OK, you'll say, it will be matter to put on more NIR device to sort out the 95% of the 5% that was left before.

Wrong.

If for some reasons the machine didn't recognize in the first separation step, there is a reason and, more than likely, it will not recognize it in the second step, the third and so on.

So, efficiency of a second machine will be way less than 95 % and up to you to state if it is convenient to go this way or do it in some different way.

What we suggest in this case is to improve the efficiency of separation into the washing line to get rid of most of contamination (all contamination separation will never happen) without pretending to get a pellet good for film or even close to this; pellets will be good for injection molding, very thick sheet and applications like these.