Independent parallel pyrolysis kinetics of cellulose, hemicelluloses and lignin at various heating rates analyzed by evolutionary computation

The kinetics of lignocellulosic biomass pyrolysis is beneficial for reactor design to efficiently produce biofuel and bioenergy. Pyrolysis is a well-developed thermochemical process that converts biomass into valuable gaseous products, bio-oils, and solid products. To understand the complex pyrolysis process of lignocellulosic biomass, three model components of cellulose, hemicelluloses (xylan), and lignin were pyrolyzed using a thermogravimetric analyzer. An independent parallel reaction (IPR) kinetic model was optimized using a particle swarm optimization (PSO) algorithm. The IPR kinetic models of cellulose, hemicelluloses, and lignin could be modeled with 1 pseudo-reaction, 4 pseudo-reactions, and 5 pseudo-reactions, respectively, and good fit qualities higher than 95% can be achieved (except a few cases for lignin). Four different heating rates of 1, 5, 20, and 40 degrees C.min(-1) were applied to examine the effect of heating rate on the pyrolysis process. When increasing the heating rate, the derivative thermogravimetric (DTG) peaks shifted to a higher temperature range, stemming from the thermal lag between the samples and heating environment. Overall, the temperature ranges of the thermal decomposition for cellulose, hemicelluloses, and lignin were within 269-394, 170-776, and 127-791 degrees C, respectively.