关键词: 反应动力学, 粉体, 安全, 热解, 生物燃料

Abstract: To explore the combustion characteristics of rice husk powder,the effect of different sizes on the minimum ignition temperature (MIT)of the rice husk powder was measured based on the experimental dust layer and dust cloud,the lower explosive limits (LEL),heat release properties and dynamic characteristics were tested by the Hartmann tube,cone calorimeter,and thermogravimetry/differential scanning calorimetry (TG/DSC),respectively. The results showed that the MIT and LEL declined with the decreasing size of the chaff powder,while the maximum explosion pressure and the rate of explosive pressure increase rose. The explosion pressure reached 0.9MPa for the sample with the size of 80~96μm,the MITs of dust layer (5mm and 10mm)and dust cloud were 130℃ and 430℃,respectively. The combustion characteristic index S_N was 3.82×10^-7,increased by 57.2% comparing to the sample with the size of 180~1250μm. The maximum release heat peak was arisen at 307s,and its intensity increased to 62kJ/m². The reaction activation energy of corresponding pyrolysis process increased from 35.35kJ/mol (sample of 180~1250μm)to 51.15kJ/mol,which demonstrated that the combustion process transformed diffusion-controlled into kinetically controlled reaction with the decreasing particle size.

Key words: reaction kinetics, powders, safety, pyrolysis, biofuel