‘Thermal shock’ technique could transform mixed plastics recycling
The process, which involves subjecting plastics to a ‘thermal shock’, means that any polymer can be broken down into its constituent monomers, said the group of scientists from the University of Warwick Engineering.
The system could signal a significant step forward in the bid to create a commercially viable technique for the recycling of mixed plastics.
The team have developed a unit employing pyrolysis – use of heat in the absence of oxygen to decompose of materials - in a fluidised bed reactor. The equipment is able to process a wide range of mixed plastics to reduce them down to products that can be retrieved through simple distillation.
Waste to chemical
“The material is put into a reactor at temperatures of between 400-500C, with or without steam injection, and the polymers are cracked back to their monomers,” said project leader Professor Jan Baeyens.
Instead of burning the plastics, the unit recycles them back to their raw materials that can be used to make the polymer again, he added.
“So it’s a waste to chemical objective rather than a waste to energy objective,” said the professor. “We give the molecules a thermal shock to crack them not burn them.”
Commercial potential
The products the Warwick team have been able to reclaim from the plastic mix include original monomers such as styrene that can be used to make new polystyrene and terephthalic acid which can be reused in PET plastic products.
Prof Baeyens said the system is extremely efficient – leading to the recovery for reuse of around 80-85 per cent of material from PET or polystyrene. Lab scale tests concluded this month successfully produced distilled liquids and solids that could be taken away for processing into new products, said the researchers.
The team leader believes interest in the system from local authorities and waste disposal firms could be huge.
“The future for this is massive,” he said. “We believe that waste to chemical is a lot more valuable than waste to energy because we recreate the original components.”
The pilot-scale unit cost between ₤60,000-70,000 (€70,000-82,000) and the team is currently working on scaling up the system to process up to 1.5 tonnes of plastics per hour.
