Lignite is a kind of coal that has high moisture content and needs to be dried before being utilized. The dried lignite will readsorb moisture during its storage. In this work, a typical Chinese lignite was dried by air at 120−180 °C and hydrothermally dewatered at 200−320 °C. The moisture adsorption isotherms of treated coal and the parent coal were obtained at 30 °C to investigate the essential moisture adsorption properties. Then the moisture readsorption performance of the studied coal in the real storage was simulated by placing the samples in the atmosphere and monitoring the evolution of the sample masses. The experimental results indicated that the moisture readsorption capacity of the air-dried lignite was lower than the parent coal and decreased with increasing drying temperature. For the hydrothermally dewatered coal, the moisture readsorption capacity increased with increasing dewatering temperature to 240 °C and then decreased significantly as dewatering temperature rose to 320 °C. The inhibiting effects of both air drying and hydrothermal dewatering at 280 and 320 °C on the moisture readsorption performance were more remarkable in winter than in summer due to the lower relative humidity. The evolution of the lignite pore structure and functional groups after the air drying and hydrothermal dewatering were also examined to understand the changes in moisture adsorption properties.

This paper describes an experimental study on the catalytic combustion of ventilation air methane in a vertical reactor. The mixture of natural gas and compressed air was used in the experiments, and the combustion products were analyzed by the Fourier transform infrared (FTIR) gas analyzer. The effects of the initial temperature, cycle time, feed gas concentration, and space velocity were studied. The experimental results show that the reactor could run under a wide range of operating conditions with self-sustaining operation and high methane conversion. Besides, it could even run with a feed gas concentration as low as 0.13 vol % without generation of CO and NO x , which has not been achieved in previous studies. The optimization of operating parameter combination increases the stability and efficiency of combustion. Different from the previous studies, the present research shows that the temperature profile of the cyclic steady state is not affected by the initial temperature. In addition, the methane conversion and reaction zone change during the process of the reaction. Thus, there is a limitation about the employment of a gas chromatograph (GC) to measure the methane concentration. Moreover, the presence of natural convection makes the temperature profiles of the cycle steady state asymmetrical.

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Lignite is a kind of coal that has high moisture content and needs to be dried before being utilized. In this article, a Chinese lignite was dried in air at 120-180 C and the changes in its physical and chemical structures after drying were investigated. The results showed that the pore volume and specific surface area of the lignite decreased after drying. Some of the methylene and methyl groups were oxidized by the oxygen in the drying air, resulting in an increase in oxygen functional groups. The combustion characteristics of the dried coals and parent coal (dry basis) were studied via thermogravimetric analysis. The total volatile yields of the dried coals increased compared to the parent coal. The burnout temperatures of the dried coals were higher than the parent coal, whereas the ignition temperatures stayed almost unchanged. An entrained flow system was set up to study the release of nitrogenous gas products during rapid pyrolysis and combustion. The HCN yields of the dried coals during pyrolysis were higher than that of the parent coal, and a similar trend was found for the NO yield during combustion. The mechanism changes of combustion and pollutant emission characteristics were discussed according to the results of the physical and chemical structure analyses.