Feedstock rapid screening for fast pyrolysis using a focused microwave beam reactor

Using fast pyrolysis processes, renewable biomass resources can be converted to bio-oils that retain as much as 75% of the original energy content, and these oils can then be upgraded to motor fuels or other commodity chemicals. In order to attain economic feasibility, feedstocks for commercial-scale fast pyrolysis must be obtained from a diverse set of low-cost resources for which the conversion performance is well-understood. This project compares the conversion performance of several feedstocks, including clean pine, whole-tree pine, hybrid poplar, tulip poplar, switchgrass, corn stover and blends of those materials, in continuous fluid bed pyrolysis systems (approximately 1 kg/hr) to that of a lab-scale 3 kW microwave fast pyrolysis reactor (approximately 2 g per batch). The performance metrics that are compared include solid, liquid, and gas yields and analysis of the liquid and gas products.

The microwave-based fast pyrolysis reactor is advantageous for parametric studies exploring the effects of feedstock material, maximum temperature, and heating rate because the individual experiments can be conducted in minutes rather than hours and substantially less material is required (2 g compared to 20 kg). Key features of the 3 kW microwave-based fast pyrolysis reactor system are (1) material heating rates as fast as 200 degrees Celsius/sec; (2) real-time temperature measurements using a Williamson pyrometer; (3) option to heat material directly using microwaves or indirectly by doping samples with graphite or activated carbon; (4) gas analysis of evolved gases using GC/MS/FID; and (5) direct measurements of solid and oil yield using gravimetric methods.