Unknown Plastic Waste Workflow

Basics

• In recycling it is best done with pre-sorting and/or labels/indicators on the plastic itself
• In most collection systems this is do-able
• The main area where this becomes an issue are small debris and/or degraded plastic
• This is common in picking up waste such as Beach Plastic
• Thus in order to aid in recycling efforts a sorting and processing workflow is needed
• This page also assumes the user does not have a Plastic Type Sensor available
• So far this page's process is mainly done via sink/float tanks, but we should also look into:
  • Air Classification
  • Froth Flotuation
  • Misc advanced cyclones and hydrocyclones (may only be effective large scale, some papers were adapting mining processing techniques)

Process Proposal 1

Basics

• Uses float/sink seperation using these media:
  • Water
  • Brine / Concentrated Salt Water
  • Oil (most likely canola/rapeseed or mixed plant oil, but any oil should work)
  • Potentially any alchohol, or sugar solution?

Pre-Sorting Processing

• Plastic is collected
• It is then held in "dirty side bulk storage" (most likely spread on tarps)
• It is then photographed to easily document composition/type of products for data gathering purposes
• It is then rinsed in water, cleaned with soap water, then rinsed to remove general dirt and salts
• Then it is shredded
• Then it is moved on "pre-sorted clean bluk storage"

Sorting

• The liquid sink/float process is used to sort the plastic in phases
• **Need to determine how to seperate #7, or if that is even in a significant concentration**

Post-Sorting

• All plastic flakes, after being sorted are air-dried by being spread out on tarps etc
• They are then put into the "sorted clean bulk storage" and/or used in the various plastic forming machines
• The remaining unknowns, and all thermosets, are then sent to be pyrolysed and/or gassified
  • See Pyrolysis Kiln

Flow Charts

• Being Placed in this Folder on User: Eric 's account for now

V1

• Was done in a discord discussion, good concept, incorrect liquid workflow

V2

• Proper liquid workflow, but used numbers instead of names, and **Does not account for type 7**
• Also does not include post brine/alchohol rinse (to return the flakes to water only), optional drying (to keep less water from entering the oil), and post oil/sugar washing

External Links

• A VERY simple lab on the process (middle school grade, but shows the concept, and uses common fluids (ie not wetting agents etc) )
• A Libretexts lab on this, has a great density table of common "pure" plastics
• A Page on the Densities of Various Alchohols (need to make a page on this)
• A Simon Fraser University Page on the Density of Common Fluids
• An "engineering toolbox" page on liquid densities
• "Recycling of plastic waste by density separation: Prospects for optimization"
• "Separation of waste plastics by froth flotation - A review, part I"
• "2 - Techniques for separation of plastic wastes"
• "Combination of three-stage sink–float method and selective flotation technique for separation of mixed post-consumer plastic waste"