Moisture Miration And Interfacial Modification Of Lignite In Microwave Dehydration Process

In order to solve the problems of high energy consumption and high reabsorption, microwave dehydration technology of lignite was applied in this paper. The lignite with four different particle sizes from eastern Inner Mongolia was treated by a self-developed microwave system under five different powers. The mathematical model for the moisture changes of lignite was developed and the relevant results were determined by finite difference method. And the computational results were in good agreement with the experimental results. The scanning electron microscope (SEM) and low temperature nitrogen absorption method were applied to study the surface features and porous structure of coal samples. Distribution of oxygen-functional groups of carboxyl and phenol-hydroxyl was evaluated based on the chemical analysis results. Readsorption experiment in constant temperature and humidity with thermogravimetric analysis were performed to study the characteristics of readsorption and spontaneous combustion. It was found that the moisture after the readsorption of the lignite dried by microwave was far lower than19.87%, the moisture after the readsorption of the lignite dried by hot air, and the ignition temperature were increased to more than295℃from275℃.The results indicated that the interfacial stability of lignite was improved by microwave, and the dehydrated lignite was difficult to reabsorb water and combust spontaneously after microwave drying. Combined with the microwave drying theory and the experimental results, the regulatory mechanism of interfacial stability of dehydrated lignite was put forward.