Reusing waste polymers
Converting mixed waste plastics and rubbers – including tyres, toys, toothbrushes and even carpets – into feedstock aromatic chemicals may be closer to reality due to technology developed by Polyflow Corporation, based in Akron, USA.
The Polyflow process works with a mixture of co-polymers and extrusions that would otherwise have gone to landfill – generally consisting of 80% PET, polypropylene and polystyrene, and 20% rubber, nylon or other specialty plastics, including PVC. The materials are heated in a tank to 538ºC until vapourised. The refined products produced from the resulting aromatics include benzene, toluene, styrene, cumene and a gasoline blend stock, which can be used in the manufacture of plastics, rubbers, adhesives and paint.
‘The process is similar to that used to crack crude oil,’ explains Joseph Hensel, CEO of Polyflow. ‘It uses a much higher molecular weight feedstock and runs at conditions that favour the formation of light aromatic hydrocarbons.’
The system can either be heated with natural gas, or using the light non-
condensable off gases and char produced during vapourisation. ‘The plant requires about 10% of the heat value of the incoming polymer waste as process fuel,’ explains Hensel, noting this compares well with oil refinery energy needs.
Thus far, the Polyflow process has proved more expensive than petrochemical
production, with operating costs of US$220/t. But with oil prices expected to rise again and through investment in upscaling, Hensel expects Polyflow to become a ‘lower cost’ method for producing aromatics.
The company has successfully run 200-300lb (90-159kg) trials of its technology since January, and is gathering investments for a US$8.5m pilot plant that will handle 2.5t/hour. The company hopes to be running a continuous process by the end of 2009.
Further information: Polyflow Corporation