Co-Pyrolysis of Woody Biomass and Oil Shale in a Batch Reactor in CO2, CO2-H2O, and Ar Atmospheres

Abstract

The partial replacement of fossil fuels with biomass provides an alternative to producing cleaner and more sustainable energy and fuels. Conventional shale oil production infrastructure can potentially be used in co-pyrolysis with biomass to reduce the use of oil shale and decrease its environmental impact. The effect of adding 10 and 30 wt% woody biomasses (spruce, alder, pine, and birch) into oil shale was studied through intermediate co-pyrolysis. The experiments were carried out in a batch reactor at 520 °C, with a 20 min residence time, in CO2, CO2-H2O 1:1, and Ar gas atmospheres. The solid products were collected and analyzed for elemental composition and surface area, while the composition of the gases was determined through gas chromatography. The difference in experimental and theoretical mass balances of fuel blends was lower than 2.5 wt% in all gas environments, indicating slight interactions between the fuels. CO2 atmospheres contributed to increased decomposition, with up to 2.6 wt% lower solid products. Biomass increased the production of combustible gases, especially CO yields, from 0.42 to 1.30 vol%. The addition of biomass and the use of alternative atmospheres can improve pyrolysis through increased fuel decomposition and a lower share of residual mass from 74.4 wt% for oil shale to 58–70 wt% for oil shale and biomass blends.