Washing Plastic (V4)
Washing plastic is essential in the recycling process and at the moment it is mostly done by hand – a very time-consuming process.
While working with plastic films I came in contact with water and plastic and the advantages but also dangers it has to offer. Shredding film has turned out to be a challenge because of overheating and dust. My only solution for this was to work with a water-cooling system. I got familiar with the dangers of microplastic in water, the dirt and chemicals, and filtration processes. I changed my focus and now I am working on everything which has to do with washing. Starting before shredding and ending with a clean and dry workable material.
Washing plastic is a very broad topic and it contains many different steps. Each of them is important and I will spend the next months on researching, experimenting and updating you guys – I hope, together with your help, we can create a way to make it possible, that small workshops are able to work efficiently and save for the environment.
Creating clean plastic demands different machines, which have to function in a workflow. Designing this process seems to me as important as designing the machines so I will also work a lot on how the different work steps could look like.
So what have I done so far:
After gathering all the information from @mathijsstroobers topic washing plastic and some research I have defined and started to work on the different steps – Cutting and prewashing, shredding with water, collecting the shreds in a mesh bag, modifying a washing machine, drying and most important filtering.
To complete the experience, we designed the bags to close with a roll-top, which compacts the plastic and creates a handle to make them easier to carry. The handle can also be used to hang the bags on a storage rack so that they can continue to air dry and are easily accessible when ready to sell.
The polyester fiber filter we first experimented with worked, but after a while it became clogged and the only way to fix that was to replace the old polyester with new polyester, which meant (A) that you’d be left with a bunch of dirty, unusable polyester and (B) you’d have to keep purchasing new polyester fiber – not ideal.
Louis found another way to filter using sand which is commonly used in pool filters – we’ve been testing it out and it seems to work pretty well. One thing that’s nice is that the sand will likely need to be replaced much less frequently than the polyester fiber did. The water in the system can be recycled repeatedly – for how long, we’re still not sure.
We know from past experiments that using the laundry machine is a good way to clean shredded plastic. Now our focus is experimenting with different bag materials and filtering methods to find what works best. Details about those elements are laid out below:
Plastic is usually shredded into some sort of bin/container. We decided to try using bags instead, since that would enable us to more easily transport the plastic granulate from the shredder to the washing machine without having to pour the plastic from one container to another, eliminating a pretty big pain point in the process.
We designed the bags to hold roughly 10 kg of plastic – about as much as a laundry machine can comfortably handle. This standard amount also makes it easy to keep track of how much plastic you’ve processed later in the process when the bags are stored – count your bags and multiply by 10 to calculate.
I am working on a line to clean agricultural mulch films on a 3-5 tons per day basis.
I am in an arid climate with scarce water resources.
I am looking at using a dry cleaning process.
Here is one company that offers a line based on heat and friction.
Here is another.
I wonder about scaling this down for smaller plastic workshops.
Hey guys I’m buying parts this weekend to on replicate your plastic washing machine. Can you provide any further specific part details? Type and capacity of water pump? How you were able to add heat with out an external hot water heater? What the diameter of the hoses you added to compensate for the higher pressures are and where these fittings/hoses had to be used? How you were able to implement your auto relay when simply turning on the machine? And please any other important details that weren’t mentioned prior. Love everything you guys do and for this positive community. 🙏🏼
We have tried a couple of experiments now, washing with bags in a machine, with just the outlet pipe fitted directly to this steel mesh filter, and it seems to flow just fine at low pressure.
However, the second-hand filter has significant wear & tear on it (will post photos soon), and we are concerned what might be let through, so would like to try building something like one of those sand filters ourselves.
@pauldufour @brunowindt what did you use at the outlet of your sand filter to stop sand from being pushed out?
The diagram posted here shows some kind of filter bar at the bottom before the outlet, and I’m wondering whether there is a specific part you can find for this, or whether to try something as simple as a sock or a wire mesh sheet secured over a pipe with holes drilled in it.
@brunowindt thanks, so if you have had wastewater emptied directly into a sump, have you taken any kind of observations or measurements about how much or what plastic or other contaminants appear/float/settle in that tank before you try to pump and filter them out?
We’ve been looking at a second-hand inline filter that someone gave us from the dairy industry, with a 2-layer reusable steel mesh filter, apparently 154 and 80 microns in size, and I wonder whether to be concerned about anything smaller being generated by abrasion.
@morayreachout exactly I designed basically a pool filter, as we need quite frequently cleaned water and the washing also needs high pressure. There might also be ways to use a gravity filter for slower washing cycles. But also I choose the pressurized filter, as I can clean it easier with backwashing.
@morayreachout Thanks for your feedback!
I am working at the moment on an updated file with all the information we have so far and I am gonna post it here as soon as it’s done.
About the sand based filter couplings, I use the big pipes for pressure reasons. About the connection to the washing machine, originally it was connected with an adapter, but the small pipe system inside the machine increased the pressure too much, so I removed lots of the “intestines” of the machine and we have a direct connection to the washing barrel now! But more to that soon!
In general, there are still many things to figure out. Especially about pre-treatment, as in label removing etc.
Also about the bill of material, we can give more detailed info later on, but it is not crazy expensive especially if you try to source things second hand etc.
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