Thermal fragmentation and pulverization behavior of lignite during the vibration drying process and its grey relational analysis of multi-factors

Abstract

Lignite particles are easy to break into smaller particles in the process of thermal drying, which affect the heat and mass transfer inside the particles. Therefore, it is important to study the fragmentation behavior of lignite for optimizing the drying process. In this article, two concepts of degree of fragmentation (F′) and pulverization ratio (R p ) were put forward to describe the overall fragmentation property of lignite after vibration drying. The results showed that the higher the drying temperature, the more favorable it was for the product particles to fragment. The impact of particle size and feeding amount on F′ and R p was relatively small, but it was still not negligible. There was a critical vibration frequency during vibration drying. Once the vibration frequency exceeded critical value, the fragmentation of particles would be greatly promoted. The grey correlation model of lignite was established to quantitatively analyze the influence of five factors on the fragmentation and pulverization of products in the process of multi-factor coupling drying. Following the grey correlation model, five factors, such as the drying time, vibration frequency, drying temperature, feed particle size and feeding amount were ranked according to their influence on F′ and R p .