Production of Liquid Feedstock from Biomass via Steam Pyrolysis in a Fluidized Bed Reactor

The nature of liquids derived from biomass fast pyrolysis is far from typical oil, and thus, different approaches for bio-oil production and upgrading are needed. In this paper the steam pyrolysis of a pine and spruce wood mixture in a bubbling fluidized bed is investigated. Particularly, the effect of steam to biomass ratio and temperature in relation to products yields and composition has been studied. Products analyses indicate that steam presence affects the yields and composition of all the products (gas, char, liquid) and promotes oxygen removal from the liquid. Increased liquid yields with significantly lower amount of carboxylic acids and higher effective hydrogen index (EHI) were obtained, which makes them more suitable for further upgrading. The levoglucosan (LGA) concentration in the produced liquid is higher compared with conventional N-2 pyrolysis, which suggests that steam pyrolylsis can be regarded as an alternative for production of fermentable sugars. Polycondensation reactions are hindered by steam presence while steam seems to act as a hydrogen donor; however, increased water content is a problem that has to be considered as well.