Flow control for plastics recycling

Mechanical recycling

Mechanical recycling is the most common approach used for recycling plastics like polyethylene terephthalate (PET) and high-density polyethylene (HDPE). Mechanical recycling refers to the processing of plastics waste into secondary raw material or products without significantly changing the material’s chemical structure.

Chemical recycling

Chemical recycling is a growing approach for plastics recycling and offers greater opportunity for scalability. In chemical plastics recycling, long hydrocarbon chains constituting plastics are broken into shorter hydrocarbon fractions or monomers using chemical, thermal, or catalytic (chemical/thermal) processes. These shorter molecules are ready to be used as feedstock for new chemical reactions to produce new recycled plastics and other chemicals. 

Chemical recycling can be further differentiated into the following categories and definitions:

1. Pyrolysis: The thermal breakdown of material without oxygen, resulting in the production of gaseous hydrocarbons that can be made into a range of hydrocarbon products including wax and oil and used as a chemical feedstock. The gas is often burnt to provide energy to the process, whereas the oil and wax can be sold.
2. Gasification: The partial combustion of material to produce carbon monoxide (CO) and hydrogen (H2), which is a mixture known as syngas. This gas can be burnt for energy or used in the production of new hydrocarbons.
3. Depolymerization: The use of chemicals to break down a polymer into its monomers or intermediate units.
4. Purification: Polymers are dissolved in a selected solvent so the polymer can be separated from any contamination before being precipitated back out and reused as a polymer.

The plastics recycling chain