Pyrolysis and CO2 gasification of biomass in high-temperature stage microscope: Morphological evolution and thermal behaviors

摘要

The morphological evolution of biomass particles during pyrolysis and char gasification was investigated by a high-temperature stage microscope (HTSM), and realistic particle shrinkage characteristics were ob-tained in combination with weight loss properties. Also, product properties were obtained on a fixed-bed and the influence of the physicochemical properties of the char on the gasification activity was consid-ered. Several typical biomass samples were selected, including poplar sawdust, rice husk, and steamed rice. As a starchy biomass, steamed rice particles underwent intense swelling at 300-330 degrees C, followed by shrinkage, and finally formed an internal loose and porous char, which was significantly different from lignocellulosic biomass. For lignocellulosic biomass, poplar sawdust and rice husk particles showed similar shrinkage processes during pyrolysis. By comparing the curves of particle shrinkage and weight loss, the development of internal pore volume of particles was reflected in a general way, which can better guide the construction of biomass shrinkage mechanism model. The gasification activity of the three biomass pyrolysis chars differed considerably and consistent conclusions were obtained in terms of particle shrinkage, weight loss, and gas products. The poplar sawdust char showed acute shrinkage of particles and loss of weight, exhibiting the strongest gasification activity, 6 times that of rice husk char and steamed rice char. The gasification activity of the char depended mainly on the degree of graphitiza-tion and was almost independent of the mesoporous structure. In the temperature range of 80 0-90 0 degrees C, higher gasification temperatures corresponded to more rapid particle shrinkage and weight loss, higher gas product yield, and greater gasification activity. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.