蔗渣的热解与燃烧动力学特性研究

As a primary energy source, bagasse has huge potential to steam or power generation in sugarcane industry. Due to its high moisture content, bagasse can cause problem of instable combustion in traditional boiler. Some new techniques have been developed to improve thermal conversion efficiency, such as gasification or co-firing with coal. The mechanism of bagasse degradation is very complex and has not been fully elucidated. This work is to describe the thermal decompose behavior of bagasse in different thermochemical processes. Non-isothermal kinetics has been proposed as an alternative to the classical determination of activation energy parameters. The dynamic thermal analysis was carried out in a Netzsch STA409 thermobalance. The pyrolysis and combustion characteristics of bagasse were obtained at different heating rates. With the Friedman method, some latent reaction mechanisms can be derived from the data analysis of non-isothermal experiments. A mechanism based on three independent parallel reactions have been used to model the pyrolysis process of hemicellulose, cellulose and lignin, with activation energy of 203.92 kJ·mol-1,238.50 kJ·mol-1 and 77.11 kJ·mol-1 respectively. Combustion process can be divided into two distinct stages, with first stage coinciding with pyrolysis process and the second one concerning a consecutive reaction of lignin pyrolysis and char combustion with activation energy of 255.57 kJ·mol-1 and 159.11 kJ·mol-1, respectively. The fitting curve of TG obtained from nonlinear regression method is coincident with experiment curves. Based on this study, it is suggested that the three major components of bagasse appear to be pyrolyzed independently with little interactions. Comparing their thermal stability, lignin is found to be most stable, the next is cellulose, while hemicellulose appears to be least stable. The results can also provide useful data for the design of a thermochemical conversion processes for bagasse utilization.