Investigation of influence of coal properties on dense-phase pneumatic conveying at high pressure

Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen were carried out in a test facility at pressures of up to 3.7 MPa to study the effects of coal type,particle size and moisture content on flow characteristics.The Jenike shear test and scanning electron microscopy (SEM) were employed to provide a better understanding of effects of the material properties on flow characteristics.Two kinds of pulverized coals,Yanzhou and Datong,with similar particle size,moisture content and density,were used in the test.Pressure drop increases with increasing the particle size at similar solid-gas ratio,superficial velocity and pressure in the receiving hopper,and pressure drops through different test sections decrease firstly and then rise with increasing the conveying velocity for the same particle size,mass flow rate and pressure in the receiving hopper.The flowability of pulverized coal decreases with increasing the moisture content in the range from 3.24％ to 8.18％.Unconfined yield strength (UYS) increases and flow function (FF) decreases with increasing the moisture content.Results of the shearing tests are consistent with the results of the conveying study.Pressure drops through different test sections are discussed and analyzed.