Flow characteristics and stability of dense-phase pneumatic conveying of pulverized coal under high pressure

Conveying characteristics and flow stability are very important for design and control of conveying system under high pressure. The influences of operating parameters (fluidizing gas flow rate and supplementary gas flow rate) and material properties (coal category, particle size and moisture content) on conveying characteristics were investigated in an experimental test facility with the conveying pressure up to 4 MPa. Wavelet transform and Shannon entropy analysis were applied to analyzing pressure drops through horizontal pipe in order to obtain stability criterion. Results indicated that with the increase in fluidizing gas flow rate, the mass flow rate of pulverized coal increased at first and then decreased while solid-gas ratio decreased all the way. Conveying phase diagrams and pressure drops through different test sections of pulverized coal under high pressure were obtained and analyzed. Conveying optimal moisture content and extreme moisture content were revealed for different coal categories. The influences of coal category and particle size on conveying characteristics were achieved. Through analyzing the relationship between Shannon entropy and conveying stability at different operating parameters and material properties, a new method for distinguishing conveying stability was established.