Center for Sustainable Environmental Technologies

The primary focus of this project is to research and develop an alternative (to fluidized bed) reactor design for the production of bio-oil.  The alternative reactor being studied is a radiative free fall reactor. 

Due to increasing energy prices and carbon emissions from fossil fuels, biomass is becoming an attractive alternative energy source as it is carbon neutral and readily available.  Typical biomasses include ground corn stalks, leaves and cobs (cornstover) and switchgrass which are somewhat difficult to handle and transport.  Iowa State University is researching and developing different systems to convert these feedstocks into bio-oil.  Bio-oil is a dark-brown, low viscosity liquid produced via thermochemical conversion of biomass using a process called fast pyrolysis. Liquid bio-oil is more easily transported and has applications in transportation fuels, chemicals and combustion for heat and power.

Fast pyrolysis is a process that is predominantly performed in a fluidized bed reactor.  It is the thermal degradation of carbonaceous material in the absence of oxygen.  Though the fluidized bed reactor boasts high throughputs and bio-oil yields the free fall reactor aims to capitalize on its inefficiencies by minimizing the use of an inert carrier gas, simplifying the design and reducing the number of moving parts.

The recently designed free fall reactor is essentially a heated, upright pipe through which biomass is fed.  The reactor is externally heated to 500°C by ceramic radiative heaters.  Biomass is ground down to small particles using a knife mill and fed into the top of the reactor with a screw feeder.  The particles fall for through the length of the pipe before they are completely pyrolyzed.  Pyrolysis vapors and char exit the reactor at the bottom.  The char is collected in a canister and the vapors are filtered before entering a condenser system.  Here the vapors are quenched into bio-oil and the non-condensable gases exit to a vent and a micro GC for further analysis.