Effect of moisture content on dense-phase pneumatic conveying of pulverized lignite under high pressure

Abstract

Moisture content has a significant impact on the conveying characteristics of dense-phase pneumatic conveying of pulverized lignite under high pressure up to 4MPa by using nitrogen as carrier gas. The objective of this work was to reveal the influence mechanisms of moisture content on the conveying characteristics in more detail and obtain a critical moisture content to distinguish the conveying stability. A set of conveying experiments of pulverized lignite with different moisture contents was carried out. The relationships among moisture content, interparticle cohesion, particle flowability and the fluidization quality of pulverized lignite were analyzed. Furthermore, a critical moisture content of flow properties was defined, and it was applied to reveal the conveying characteristics and the conveying stability of the whole system, suggesting that it can be considered as a good indicator to distinguish the conveying stability. Meanwhile, a simple and effective method to find out the critical moisture content was developed in this work. For pulverized lignite in this paper, the critical moisture content was determined to lie in 14.20wt.%–14.44wt.%. When moisture content is below it, the mass flow rate decreases slowly as moisture content rises, and the conveying process is stable and controllable; above it, the mass flow rate shows a sharp decrease with the increase of moisture content, and the conveying process becomes no longer stable.