Theoretical and Experimental Study on Spontaneous Ignition of Lignite during the Drying Process in a Packed Bed(PDF)

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• Date:2025-04-30
• Title of Paper:Theoretical and Experimental Study on Spontaneous Ignition of Lignite during the Drying Process in a Packed Bed(PDF)
• Journal:Energy Fuels
• Summary:Lignite is a kind of coal which has high moisture content and needs to be dried before being utilized. Lignite has a great spontaneous ignition tendency due to its high volatile content and porous structure. Spontaneous combustion may take place if heat accumulates within the coal layer due to low temperature oxidation, presenting a serious risk during lignite drying. In this paper, a calculation method is developed to predict the spontaneous ignition of lignite during the drying process in a packed bed dryer. The basic principle of this method is that the spontaneous ignition is determined by the combination of convective heat transfer between the gas flow and the particles and the heat generated by the oxidation reactions. The heat generation can be obtained from the differential scanning calorimetry (DSC) curve of the thermogravimetry combustion experiment. The heat loss is obtained by calculating the heat transfer coefficient between the lignite particles and the gas flow. Hence, provided the temperature, the velocity, and the oxygen concentration of the drying gas, together with the size parameters of the particles and the bed, are given, whether the spontaneous ignition occurs or not can be predicted. Moreover, the critical inlet gas temperature, below which the spontaneous ignition will not occur, can be determined as long as the DSC curve is obtained. Numerous experiments have been carried out in a lab-scale reactor. The experimental results were used to verify the calculated results, and the deviations are acceptable.
• Co-author:Xuezhong Gao,Chengbo Man, Shangjian Hu, Xueyuan Xu
• Volume:26
• Page Number:6876−6887
• Translation or Not:No
• Date of Publication:2012-10-09