Fluidized bed gasification of plastic waste and residual biomass – an overview of HTW® and Chemical looping technology development

Mechanical recycling of plastic waste to second generation products is the currently mostly applied technology to reuse the valuable elements contained, particularly carbon, but often leads to a loss in product quality. Furthermore, its economic potential is limited due to heterogeneous waste streams, and the remainder - non-recyclable composites - is disposed in landfills or thermally utilized with the challenge of carbon capture. In contrast, chemical recycling preserves the carbon and other elements such as hydrogen by transforming them into valuable base chemicals or synthetic fuels. This enables a circular economy, which is a key factor in achieving a net-zero emission society. Thus, the Institute for Energy Systems and Technology at the Technical University of Darmstadt is investigating the promising path of fluidized bed gasification processes with downstream gas cleaning and synthesis at pilot scale. Its 1 MWth modular pilot plant allows for different process configurations as bubbling bed, circulating bed and dual-fluidized bed gasification under autothermal conditions. The whole process chain from the waste to a valuable product such as methanol or Fischer-Tropsch has been demonstrated and optimized in test campaigns of several weeks. Based on these pilot tests, an upscaling to industrial scale is conducted in combination with modelling and simulation. Expertise has been built up from 2015 in the High-Temperature Winkler (HTW®) gasification of lignite, where meanwhile residual feedstock as biomass and plastic waste (solid recovered fuel = SRF) have been proven to be suitable. Chemical looping gasification (CLG) was demonstrated successfully and investigated for the first time at pilot scale in 2022 at the institute using biogenic residues as feedstock.