Effects of heating rate and gas atmosphere on the pyrolysis and combustion characteristics of different crop residues and the kinetics analysis

Efficient utilization of crop residues can help to solve the problem of global resource scarcity. The pyrolysis and combustion characteristics of 40 crop residues and 3 lignocellulosic components in different atmospheres by thermogravimetric analysis were analyzed. The results showed that with the increase of heating rate, the pyrolysis and combustion of cellulose, hemicelluloses, lignin and crop residues shifted to higher temperature zones. Meanwhile, the comprehensive combustibility index increased significantly, indicating that a higher heating rate could intensify and improve the pyrolysis and combustion performances. At the heating rate of 20 degrees C/min, the variation ranges of ignition temperatures of crop residues in N-2, air and O-2 were 253-295 degrees C, 247-275 degrees C and 245-268 degrees C, and the variation ranges of burnout temperatures were 555-682 degrees C, 466-596 degrees C and 323-357 degrees C, respectively. The comprehensive combustibility index in O-2 was 144.24 x 10(-7), which were much higher than those in air and N-2. The variation ranges of activation energies of crop residues were 25.52-36.84, 27.96-43.35 and 41.07 -69.35 kJ/mol in N-2, air and O-2 at 20 degrees C/min, respectively, and the combustion of crop residues in O-2 is the most intense. Overall, rape stalk showed the best comprehensive pyrolysis and combustion performance, and rice straw was the poorest. (C) 2019 Elsevier Ltd. All rights reserved.