Combustion Characteristics of Fast Pyrolysis Oils Derived from Hybrid Poplar

Abstract

A laminar-flow, single-droplet combustion facility has been used to evaluate the fundamental combustion properties of biomass pyrolysis oils produced by a fast, ablative vortex reactor at the National Renewable Energy Laboratory (NREL). Earlier single-droplet combustion experiments with pyrolysis oils derived from several biomass feedstocks (pine, oak, & switchgrass) revealed that droplets of these oils undergo violent microexplosions after relatively little mass loss, followed by disruptive, sooty burning and, for some oils, coke particulate formation. The present research focuses on the combustion behavior of three oils produced using the same hybrid poplar feedstock, but slightly different reactor and hot-gas filtration process variables. Surprisingly, the burning rates, degree of sooting, and coke particulate generation of these three poplar oils are found to differ considerably, presumably as a result of varying extents of fuel vapor cracking during the production of the oils. These results suggest that pyrolysis process conditions play a dominant role in the combustion behavior of the collected oils. A further implication is that, with adequate pyrolysis process control and possibly water or alcohol addition to the collected oil, a biomass pyrolysis oil may be produced which is optimized for fuel handling and combustion characteristics.

This work was sponsored by the U.S. DOE’s Office of Utility Technologies, Office of Solar Thermal and Biomass Power Technology, Biomass Power Program, and through direct support of the National Renewable Energy Laboratory, Golden, CO.