(684a) Ablative Pyrolysis of Beetle-Killed Trees

Authors: 
Luo, G. - Presenter, University of Washington
Resende, F. - Presenter, University of Washington

In the western United States, around 42 million acres of conifer forests have been infested by bark beetles since 1996 and this number is expected to increase in the near future. This high level of tree mortality caused by bark beetle epidemic has already negatively impacted public benefits from forests; therefore, beetle-killed trees should be properly disposed of. However, some undesirable properties (e.g. bluish discoloration and cracking) of beetle-killed trees limit their applications for solid wood and wood panel manufacturing. Nevertheless, low moisture content and therefore high energy content make beetle-killed trees attractive feedstocks for fast pyrolysis. Our previous research using Py-GC-MS/FID showed that the decay stages of beetle-killed lodgepole pine (Pinus contorta) did not significantly affect the performance of both non-catalytic and catalytic fast pyrolysis, indicating fast pyrolysis is a promising way to convert beetle-killed trees into high-value chemicals and fuels. Here we designed and constructed a novel lab-scale ablative reactor to perform the fast pyrolysis of beelte-killed trees, producing high yield of bio-oil, which could also be extended for other types of biomass. The ablative pyrolysis unit consists of a hot plate and rotating wood chip bowl. Ablative pyrolysis of biomass occurs as intimately contact with the hot plate surface. Then, the generated pyrolysis vapors are quickly swept out of the reactor by the nitrogen carrier gas for further rapid cooling and condensation. Compared to the other pyrolyzer configurations, an obvious advantage of our reactor is that the reaction rates are not limited by the heat transfer through the biomass particle and thereby in principle there is no upper limit to the biomass particle size that can be processed. High costs of grinding of biomass can be reduced in our reactor system. The final goal of this unit is to simulate the conditions found for fast pyrolysis in a mobile ablative pyrolysis unit. Since biomass usually has a low bulk density thereby low energy content compared to bio-oil, using mobile unit to convert biomass into bio-oil near the harvesting point can also help reduce the transportation costs. Although ablative reactor is mechanically driven and the process is surface area controlled, the scale-up issues are less of a concern when small mobile pyrolysis units are considered. In this talk, we will show a systematic study on the fast pyrolysis of beetle-killed trees using the ablative reactor we designed. Different operating parameters including temperature, contact pressure, rotating speed, and biomass particle size will be tested to optimize the bio-oil yield. Their effects on the qualities of products will also be presented.