Hydrogen-rich gas production by continuous pyrolysis and in-line catalytic reforming of pine wood waste and HDPE mixtures

Abstract

The continuous pyrolysis-reforming of pine sawdust and high density polyethylene mixtures (25, 50 and 75 wt% HDPE) has been performed in a two-stage reaction system provided with a conical spouted bed reactor (CSBR) and a fluidized bed reactor. The influence HDPE co-feeding has on the conversion, yields and composition of the reforming outlet stream and catalyst deactivation has been studied at a reforming temperature of 700 °C, with a space time of 16.7 gcat min gfeeding 1 and a steam/(biomass + HDPE) mass ratio of 4, and a comparison has been made between these results and those recorded by feeding pine sawdust and HDPE separately. Co-feeding plastics enhances the hydrogen production, which increases from 10.9 g of H2 per 100 g of feed (only pine sawdust in the feed) to 37.3 g of H2 per 100 g of feed (only HDPE in the feed). Catalyst deactivation by coke is attenuated when HDPE is co-fed due to the lower con- tent of oxygenated compounds in the reaction environment. The higher yield of hydrogen achieved with this two-step (pyrolysis-reforming) strategy, its ability to jointly valorise biomass and plastic mixtures and the lower temperatures required compared to gasification make this promising process for producing H 2 from renewable raw materials and wastes.