Pyrolysis and kinetics characteristics of typical crop biomasses

It is necessary to study the process of biomass pyrolysis in order to use it efficiently. The pyrolysis characteristics and pyrolysis kinetics parameters of four typical crop biomasses (rice shell, rice haulm, corn core and corn haulm) are studied using thermogravimetric analysis (TGA). Results indicate that biomass pyrolysis process may be divided into three stages: the preheating dry stage, the volatile matter separation stage, and the carbonization stage. Thermal weight loss mainly occurs at the volatile matter separation stage. Because the biomass has higher volatile matter and lower fixed carbon, its pyrolysis is quite thorough. The rank order of the synthesized pyrolysis characteristic index is rice shell, corn core, rice haulm, and corn haulm. At the same time, the pyrolysis process can be divided into two stages. The volatile matter separates out fiercely in the initial pyrolysis period with an obvious peak and lower activation energy, while there is no obvious peak and the activation energy reaches higher in the later pyrolysis period. For coal residue, because of its lower volatile matter and higher ash, the ash hinders the volatile matter proliferation to a certain extent in the initial pyrolysis period, causing difficulty in separation of the volatile matter. Secondary volatile matter separations concurrently happen near the end of the pyrolysis period. The pyrolysis characteristics of sludge is similar to biomass. In addition, the pyrolysis reaction follows the R2 model for rice shell and corncob in the first prolysis stage. The pyrolysis reaction is in line with a response model for the other biomasses and the rest various stages. The threedimensional spherical symmetry subordinates to the proliferation mechanism for coal residue in the initial pyrolysis stage. The pyrolysis reaction is governed by the liquefaction reaction. The progression of chemical reaction is 3/2 in the later pyrolysis stage. The sludge adheres to the simple reaction order mechanism.

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