Microwave pyrolysis of corn stover: Process development and reaction kinetics

I&EC 50

Fei Yu1, Zhiping Le, lzping@ncu.edu.cn2, Shaobo Deng1, Paul Chen1, and Roger Ruan1. (1) Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave, Saint Paul, MN 55108, (2) Department of Chemistry, Nanchang University, 999 Xuefu Road, Qianhu, Nanchang, 330031, China
The present study was to investigate the microwave-assisted pyrolysis of corn stoves in nitrogen gas environment. The yields of syngas, bio-oils, and solid residue obtained at different input power were determined. Under our experimental conditions, a power input level above 300 W was necessary to initiate thermal pyrolysis of corn stover. The degradation of solid corn stover increased with increasing microwave power. A higher power input also favored syngas production. Adding 1% pyrolytic residue to the corn stover pyrolysis increased the yields, particularly the liquid fraction yield. Addition of sodium hydroxide (NaOH) to the corn stover as catalyst increased the syngas yield greatly. The chemical profiles of the syngas and bio-oils were determined using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). A thermogravimetric analysis (TGA) including determination of kinetic parameters was performed over the temperature range of 373-1073 K at controlled heating rates of 10 - 30 K/min and with various particle sizes. Under the conditions studied, the heating rate has a significant effect on the pyrolysis process while the particle size has little effect on it. One-step global model was developed to simulate this pyrolysis of corn stover and to determine the kinetic parameters. Although various chemicals were released during pyrolysis, one-step global kinetic is looked to as offering a clue to the key mechanistic steps in the overall degradation process.