Plastics chemical recovery for production of chemical intermediates at a Swedish chemical complex

Report, 2016

The present report discusses process concepts for chemical recycling of waste streams for production of chemical intermediates at a Swedish chemical complex site.
The total Swedish waste stream of plastics, automotive shredder residues (ASR) and electronic waste (WEEE) currently sent to energy recovery were considered and metal recovery was also considered for the relevant streams. Forest residues were also used as an input following a vision of feedstock flexibility and carbon-neutral production of chemicals.
The layout of the envisioned waste-to-chemical plant includes a process for production of ethylene via gasification of plastics and forest residues and a process for production of syngas for OXO-synthesis applications via pyrolysis of ASR and WEEE.
Mass and energy balances were established by process flowsheet simulations and process integration opportunities were identified by applying an energy targeting methodology. Finally, the GHG emission reduction potentials of such processes were quantified by keeping the energy recovery alternative as reference of comparison.
Based on rather optimistic assumptions it was found that about 120 kt of ethylene per year and about 44 kt of syngas can be produced which are respectively about 15% and 26% of the site demand of ethylene and syngas to OXO synthesis.
Overall, the estimated contribution to global GHG emission reduction lies in a range between 800 and 1300 kt CO2-eq per year depending on the different scenarios of marginal technologies for production of ethylene, electricity and heat. This is about the same order of magnitude of the current on-site GHG emissions at the Stenungsund chemical complex site. This result is based on the assumption that chemical recycling is alternative to energy recovery which in Sweden is done in CHP units connected to district heating networks. By diverting waste to chemical production, we assumed that biomass CHP units compensate for electricity and heat production and that this can even create a surplus of electricity in short term which in turns reduces the production of electricity in coal power plants. This results highlights that the climate consequences of the proposed recycling strategy are largely dependent, at least in Sweden, on the future development of the biomass prices and utilization.
The results also show that an important reduction of GHG emissions can be obtained by recovering the large amounts of excess heat available from the thermochemical processes for production of steam which can be exported to the various chemical plants by appropriately placing the proposed processes close to or in the middle of the chemical complex site. This steam is about 70% of the steam currently produced at the site in natural gas boilers. The reduction of natural gas consumptions in steam boiler contributes to about 20 to 30% of the total GHG emission reduction potential which highlights the suitability of the Stenungsund site for large-scale implementation of biorefineries and waste-to-chemical plants.