Mixing of Fast Pyrolysis Oil and Black Liquor : Preparing an Improved Gasification Feedstock

Co-gasification of fast pyrolysis oil and black liquor can be used to increase the size and improve profitability of pulp mill integrated biorefineries. The acids present in pyrolysis oil limit the amount that can be mixed into black liquor without causing precipitation of the black liquor dissolved lignin. This work shows that a simple model based on pyrolysis oil total acid number, including weak phenolic acids, can be used to predict the maximum pyrolysis oil fraction in blends. The maximum oil fraction is 20-25% for typical pyrolysis oil but can be increased up to at least 50% mass, corresponding to 70% energy, by addition of base. Thermodynamic equilibrium calculations are used to understand the effects of blend composition, including any added base, on the performance of a commercial scale gasification process. A substantial increase in overall gasification efficiency is observed with increasing pyrolysis oil fraction.Funding details: Luleå Theological University, LTU; Funding details: Energimyndigheten, 38026-1; Funding text 1: This work was supported by The Swedish Energy Agency (through grant 38026-1) and the industry consortium in the LTU Biosyngas Program. Yrjö Solantausta, Anja Oasmaa, and co-workers at VTT are gratefully acknowledged for FPO samples produced in the VTT fast pyrolysis pilot and pyrolysis oil analysis. BTG Biomass Technology Group is acknowledged for providing FPO samples. Albert Bach Oller at LTU is acknowledged for bomb calorimetry in the LTU Energy Technology Lab. Urban Lundmark at Smurfit Kappa Kraftliner Piteå is acknowledged for data and discussions regarding BL residual alkali.</p