Chemical recycling

Fraunhofer develops thermochemical processes for the recycling of mixed or heavily contaminated plastics and composite materials.

Chemical recycling of plastics

Chemical recycling (feedstock recycling or raw material recycling) has the potential to recycle even highly contaminated and problematic plastic waste, e.g. composite materials oder mixed plastic feedstocks. It thus represents a supplement to mechanical processes of plastics recycling.

Chemical recycling at Fraunhofer UMSICHT

© Fraunhofer UMSICHT
Chemical recycling: from waste materials from composite materials to basic chemical materials

At Fraunhofer UMSICHT in Sulzbach-Rosenberg, we primarily develop thermochemical conversion processes (e.g. pyrolysis) as well as preparation and purification processes for intermediate products resulting from the recycling of plastics.

Objective: Plastics in virgin quality

The aim of thermochemical conversion is a depolymerization of plastics by splitting the polymers into monomers, i.e. low-molecular chemical basic components. The resulting compounds, which can be found in the pyrolysis oil or gas, can be polymerised again. The resulting basic chemicals are suitable for the production of plastics in virgin material quality.

Chemical recycling with the iCycle platform

© Fraunhofer UMSICHT
iCycle demonstrator for the thermochemical preparation of composite materials
iCycle demonstrator for the thermochemical preparation of composite materials

With the iCycle platform developed by Fraunhofer, feedstocks containing plastics are pyrolyzed under an oxygen-free atmosphere at temperatures above 500°C. The decomposed polymers accumulate in the pyrolysis products oil and gas and can be extracted from them. With the iCycle platform for chemical recycling, Fraunhofer has facilities on a demonstration scale.

Innovative heat exchanger technologies

The iCycle pyrolysis differs from other pyrolysis technologies mainly by patented, novel heat exchanger technologies, which on the one hand ensure an energy-efficient operation of the plant and on the other hand enable an optimal heat transfer to the input material and the best possible temperature control.

1st focus: Problem plastics and composite materials

© Fraunhofer UMSICHT
Shredder fraction from the processing of electronic waste

One focus of Fraunhofer UMSICHT's work in chemical recycling is on problematic, heavily contaminated or polluted plastics and composite materials that are difficult to recycle, e.g. CFRP and GFRP (wind turbines, rotor blades), thermosets, resins or residues from the processing of electronic scrap (e.g. printed circuit boards) and end-of-life vehicles and other products (e.g. brake pads, air filters, bicycle-frames, boats).

Extracting basic chemicals from pyrolysis oil

Such plastic fractions are often rich in aromatic compounds. These aromatic compounds are found in the pyrolysis oil. This could be validated several times by GC-GC-MS analyses. Under certain conditions it is economically reasonable to extract these chemicals directly from the pyrolysis oil.

Fraunhofer offers promising technological approaches here: For example, it has already been possible to produce a styrene concentrate from glass fiber-reinforced plastic waste, which has been polymerized back into polystyrene. From printed circuit boards, a phenol-rich oil could be produced, from which phenol was recovered in crystalline form (> 99 % purity).

2st focus: preparation and purification of pyrolysis oils

© Fraunhofer UMSICHT
The preparation and purification of pyrolysis oils (here from biomass residues to fuels) is one of the core competencies of Fraunhofer UMSICHT

In the field of aliphatic oils (e.g. from plastics such as PP, PE), which are primarily used for the production of crude oil-like products or for fuel synthesis, the aim is to improve the quality of these oils for further industrial processing, e.g. in a steam cracker.

Dehalogenation of pyrolysis products

Fraunhofer is developing the optimum processing and purification processes for pyrolysis oils, particularly with regard to the removal of impurities and pollutants.

One focus is on the elimination of halogen-containing organic compounds (dehalogenation). By cracking with the aid of hydrogen-rich compounds, for example, halogen-carbon bonds are split and finally removed from the pyrolysis oil as harmless halogen salts.

Background and technologies: Chemical recycling

From waste to new product: Chemical recycling (also known as raw material recycling or feedstock recycling) has the potential - as a supplement to mechanical recycling - to achieve a more efficient use of plastic waste as raw material. Plastics that are currently not recycled can thus be reused as an alternative to incineration.

The aim is to close the value chain from plastic waste to recycled virgin material, especially for sensitive product areas such as food packaging, toys or medicinal products.

Of the 6.1 million tonnes of plastic waste generated alone in Germany in 2017, 2.8 million tonnes were materially recycled. 3.2 million tonnes were energetically recycled, i.e. most of it was incinerated. These were mainly mixed plastic waste and sorting residues from mechanical recycling.

Plastic impurities prevent recycling

Contamination of the plastics by glass, metals, fibres, wood, paper, pigments, additives or flame retardants also makes recycling more difficult, because the range of application of the recyclates produced is severely restricted. Especially in these material flows, chemical recycling should be considered, because it offers the chance to obtain chemical basic materials for plastics production from these fractions. If the raw materials can be provided in virgin material quality and free of any impurities and pollutants, plastic products can be reused in the future without cycle limits.

Technology Overview Chemical Recycling

Possible technological processes for chemical recycling include solvent-based processes such as solvation or solvolysis, but also hydrothermal microwaves and thermochemical processes (pyrolysis, gasification). The choice of the respective process depends strongly on the composition and contamination of the feed material.

Pyrolysis enables decentralised plant operation

Thermochemical processes are particularly suitable for highly mixed and contaminated material flows. One advantage of pyrolysis in particular over gasification is the possibility of decentralised operation.

Fraunhofer UMSICHT in Sulzbach-Rosenberg looks back on many years of experience in the field of thermochemical processes. With the iCycle® technology, it has already been possible to convert complex material flows such as electronic scrap and composite materials on a demonstration scale (70kg/h) and recover fibers, minerals and metals in the process.

In the field of biomass conversion, the TCR technology provides a platform for the synthesis of green crude oil for power or hydrogen production.

more details

Interview with Dr. Alexander Hofmann

»Thanks to pyrolysis, even problematic plastics can be recycled«