In recent years, the world has witnessed a rapid rise in waste production and energy demand, which has increased interests in waste to energy processes, particularly the co-pyrolysis of wood and plastic waste. Nonetheless, for plastic waste, most research studies narrowly focus on polyolefins because of their abundance in waste streams and their high oil yields from pyrolysis. In this paper, we study the co-pyrolysis of non-polyolefins polystyrene (PS) and polyvinyl chloride (PVC)-and poplar wood (PW), in order to investigate the synergistic effect of PS and PVC content on product yield, gas specie yield and heating value. The experiments were performed using a fixed-bed reactor, heated to 750°C at a rate of 20°C/min under nitrogen atmosphere. Our results show that PVC has a large positive synergy on char yield with a maximum value of 8 wt% at 30 wt% PVC content, whereas PS only showed a slightly positive synergy (2.5 wt% maximum). Concerning oil and gas production, PS provides a small synergy. However, PVC showed a significant positive synergy on oil yield with a maximum value of 11 wt% at 50 wt% PVC content, which was linked to a strong negative synergy in gas production. Regarding gas specie yields, the addition of PS led to positive synergies in the formation of H 2 , CH 4 , CO and CO 2 , although insignificant interactions were observed for C H x y compounds. Furthermore, by comparing the distribution of chloride species in the products of co-pyrolysis with PVC, using experimental and theoretical methods, we discovered that the negative synergy in HCl yield observed was mainly due to the dissolution of HCl in the water fraction of the condensed oil phase, rather than the formation of chlorinated organic compounds, as suggested in previous literature works. Our study therefore consolidates the understanding of the synergistic interactions between wood, PS and PVC co-pyrolysis, under conditions that favour gas production.

Syngas production via the pyro-gasification of waste biomass is a promising means of managing waste while producing renewable fuel. However, such waste may contain a significant level of impurities such as chlorine, which may result in hydrogen chloride (HCl) being formed in the syngas produced. The presence of HCl gas may increase the risk of corrosion and may be harmful to health and to the environment. Consequently, stricter limits on HCl concentration in syngas are being imposed by environmental regulations and syngas end-use specifications, which is driving the search and development of more efficient and cost-effective methods of eliminating HCl. One such method is dry adsorption using inorganic sorbents. In literature, the majority of sorbents studied are based on commercialised products, and thus, there lack studies on the use of waste-derived sorbents for treating HCl in syngas. Therefore, this paper presents an experimental study on the adsorption potential of the solid waste sorbent, CCW-S, which is compared to that of the commercial sorbent, Bicar. Various physicochemical analyses were performed on the sorbents before and after the tests, including ICP, FTIR, XRD and TEM-EDX. The first set of adsorption tests were performed using a gas mixture of 500 ppm HCl in nitrogen (HCl/N 2 ) at ambient conditions (25 °C, 1 atm). The results revealed that Bicar was the better performing sorbent with an average breakthrough time of 66 h and a HCl adsorption capacity of 27 wt%, whereas the performance of CCW-S was lower (7.8 h and 4 wt%). Furthermore, TEM-EDX images of CCW-S particles show the participation of the impurities-Al, Fe, and Mg-in HCl capture. When the second set of adsorption tests were conducted with a simulated HCl/syngas atmosphere, a significant decrease in sorbent performance was observed, which showcases inhibitory interactions occurring between syngas and the sorbents, in relation to HCl adsorption. The results of this preliminary investigation reveal a promising opportunity to valorize industrial residues as cheap and efficient sorbents for the removal of HCl in syngas. This will enable a wider market penetrating of waste-derived syngas, while meeting the quality requirements of increasingly strict environmental regulations and end-use devices.

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