Center for Sustainable Environmental Technologies

Fast pyrolysis is a rapid (few seconds), mild temperature (about 500°C) process that converts biomass into gas, solid, and liquid products. Pyrolysis gas is a low heating value gas that can be employed to provide process heat. Bio-char, which can comprise up to 20 weight % of the product, has similar characteristics to charcoal; it can be employed as substitute for coal (as fuel), but more promising options involve farm land fertilization and carbon sequestration. Finally, bio-oil (more than 70% weight yield possible) is a highly viscous, dark liquid composed of numerous organic components. Bio-oil can be upgraded to transportation fuels through various processes and therefore holds great promise as a biomass densification agent. By densifying biomass into bio-oil, transportation costs, which could limit the size of biomass based refineries, would be drastically reduced.  An economic analysis on distributed small fast pyrolysis plants vs. a large centralized fast pyrolysis plant has been conducted and reported.

Gasification is less rapid, higher temperature (800-900°C) process producing a synthesis gas and solid char.  This part of the project is researching the feasibility of a 2000 dry ton per day biorefinery with biomass pretreatment setups including drying and grinding, gasifier setups including high and low temperature (slagging and non-slagging), synthesis gas cleaning setups including hot and cold gas cleaning, and fuel synthesis setups including Fischer-Tropsch and methanol-to-gasoline catalytic processes.  ASPEN PLUS™ (Advanced System for Process Engineering) software is being used to simulate the system and generate a visual representation of the mass and energy balances whereby optimization can occur.  From there sizing and costing of equipment can be completed.  Sensitivity analysis whereby a process parameter (such as feedstock cost, feedstock moisture, level of recycle streams, or catalyst cost) is varied across a range resulting in a range of fuel production costs.