Sorting Plastic from Paper

Too bad the input stream wasn't already segregated into paper vs. plastic....

Doing this beforehand is better than afterhand.

I know, this is how the material is received. The main bottleneck is the size of the material post shredding...makes NIR sorting hard and expensive.

Kudos for trying to do a good job with this, even though you are now dealing with a difficult mixed stream, and trying to sort it out afterward. Once this varied input is chopped into ~1cm particles, I don't know what color, reflectivity, density, or other qualities would be able to distinguish paper from plastic, and send each to a separate stream. Other contributors may know this, and with luck we may hear from some.

Your situation reminds me of a recycling operation that occurred in my former home town (Yakima, WA, USA). A block up the street from where I lived, there was a guy on a corner lot who set up a collection center. It consisted of about eight wooden fruit bins (about 1.2m x 1.2m x 0.6m tall) nestled behind some hedge landscaping. Everyone in the neighborhood was invited to bring recyclable items, which were self-sorted into the bins by three colors of glass, slick vs. newsprint paper, and some kinds of plastic. This whole operation was very clean and odor-free, and as "green" an effort as I have ever seen.

But then guess what. Other "greenies" thought this was a nuisance eyesore (it definitely was not), and had it closed down.

For this reason, among others, I have come to view "environmentalists" as mostly troublemakers who have no genuine concern about the environment, but rather are Luddites who out of envy, or other foul motivation, would roadblock any successful operation, including efforts they really ought to like.

A type of heated windsifter if I understand right. We have been looking into heated conveyor belts also, plastic softens (sticks to belt) and paper flies off the end...somewhat the same principle.

Thanks for the tip, any idea if this is done yet in industry?

Except you have to scrape the belt and get "a glob" of "something".

If you work out the flows and velocities, the different polymers will precipitate as a function of mass, type and in a zone, distance wise.

And you can't know everything for nothing, but if you dig long enough, you could find out.

Hello, I am working on segregation of Plastic from waste so as to reduce manpower that get wasted as ragpickers. I am thinking of using density property here like if we put waste in water heavy materials like biodegradable, metal piece get settle down and what we see the plastic and paper and some light material would be floating.I want to know how can I use basic science here.

Is the extra time or money worth it to reclaim it for recycling? I believe that recycling is the reason you wish to separate it. There comes a time when adding additional cost is not economical. My thoughts are burn it to generate electrical power if you have significant source of it.

Many will say that's not a very green approach or solution. I ask how much more energy are we going to expend to reclaim it? Would that energy cover producing new? How many barrels of oil will burning to produce electricity save as we would have to source the power from some fuel.

Taking a shot in the dark here but if there is a difference in the densities of each component you might be able to run the mixture through a liquid where the lighter would float to the top

well, having seen how paper is made, if the entire lot is cycled into hot alkaline water and beaten the paper will return to the loose fiber stage but the plastic will remain. With a long enough time you can even turn carboard boxes into fibers, the fibers can be rinsed through coarse screens that will trap the plastic and the fibers can be caught on flyscreen sized mesh and the water recycled. At days end you will have 2 streams.

The main advantage is that it can be operated with very little hand work, the pumps etc are common process pieces. The wet pulp can be sold off to people that make dozen egg holders of the type that are obviously made this way. You can make your own dozen egg cartons. A lot depends on the volume you have of this stuff.

Just putting an idea into the mix, how about you immerse the whole lot into warm to hot water so that the paper softens to a mush and then put the whole lot into a centrifugal sieve?

This way the paper mush will excrete through thte holes but the plastic particles will not, obviously only if the holes are too small for the plastic but large enough to allow the paper mush through.

Steve

I'd shred to a near uniform size. Run the mix through a tank of water, water adds weight to the paper, not so much to the plastic. Remove from the tank and place in a tumbler to keep things from clumping together too much. With one item now considerably heavier than the other use several streams of air to "fluff" and separate the two. The lighter particles would float up and be drawn off with vacuum pressure.

It's not 100% but it would be fairly quick.

Good luck.

GA. I was going to suggest soaking then winnowing.

Another idea might be to look into a sorting via vertical air flow. I suspect that in some of your pieces, the plastic is adhered to the paper so you have some specific issues that would require the water as some have suggested. But the vertical flow of air within a large cylinder does somewhat of a separation. It is used for sorting all the coupons that come in from super markets by some folks but I have not personally seen it in action.

Dear Sir,

My suggestion may be of some help provided there is signeficant defference in the density of plastic and cardboard.

I am not aware if you have seen a wheat thrasher working. In a wheat thrasher there a fan installed below the droping mixture of wheat and straw. The wheat drops at small distance from its original path and collected in a bag, while the straw is taken a long way towards the flow of air. Same way the card board being heavier will drop closer while the plastic scraps will drop far off the stream and hence can be routed in the desired channel.

The same may work for plastic & paper mixture, but speed of fan need to be controlled very precisely, but I am not sure if it will works for paper & plastic mixture.

-Dr N P Singh

Because the quality and variability of the material the ability to salvage is very low. The amount of energy and water needed to separate just paper from plastic is counterproductive. Separating types of plastic is virtually impossible at the point you are describing and is therefor is of little salvage value. I argue for emerging gassification technologies which can convert these materials as well as many other organic feedstocks into electrical energy or bio-fuels and both of which are a carbon neutral source of energy.

I am facing a similar problem. Have you managed to find a solution in separating plastics from paper?

Regards

Kyriacos Kyprianou