Effect of gypsum waste inclusion on syngas production during CO2-assisted gasification of waste tires

Abstract

Syngas production from co-gasification of waste tires and different amounts of drywall waste gypsum (CaSO4) was investigated using CO2 as the gasifying agent in a lab-scale reactor. Gypsum is known to react with carbon feedstocks through solid–solid reactions to produce CaS and CaO, CO, and CO2. The presence of gypsum in waste tires increased the syngas yield from the conversion of char and tars. Gypsum addition to the waste tire also increased syngas quality from increased syngas energy yield. The overall yield of syngas increased by up to 55% while the energy yield (MJ/ kg feedstock) improved by 40% with gypsum addition. The product gas yield, energy, H2, and CH4 yields increased with gypsum addition while CO only increased for lower gypsum concentrations. Higher gypsum addition increased CO2 yields. Aspen Plus simulation results revealed that for waste tires, temperatures < 1200 °C suppressed the transformation of sulfur present in gypsum into SO2 for all waste tires to gypsum feed mass ratios. At 50 wt% gypsum concentrations, only 2% of the sulfur in the feedstock was transferred into SO2. The results showed improved syngas yield and quality, without any increase in sulfur emissions showing the benefits of gypsum waste incorporation in waste tire gasification.