Research on Resistance Properties for Dense Phase Pneumatic Conveying of Pulverized Coal in Vertical Pipe at Different Pressures

Abstract

Experiments on pressure drops in vertical pipe in dense‐phase pulverized coal pneumatic conveying system were conducted under the pressure range from 2.1 MPa to 3.6 MPa. The nitrogen, as conveying gas, was introduced into the system via a header connected with sixteen nitrogen cylinders. Gas flow rate was controlled with a needle valve, and three flow meters were used to measure the volume flow rate of nitrogen. The dosing hopper was suspended on three load cells, which enable on‐line weighing the solids collected in the hopper. Pressures and pressure drops were measured with pressure transducers and KELLER differential pressure transducers, respectively. All the signals were connected to a computer. Sampling time interval was from 5 milliseconds to 1 second.The experimental results indicate that at the pressure range from 2.1 MPa to 3.6 MPa when the solids mass flow rate is kept constant and the superficial velocity increases, the pressure gradient first decreases, then starts to increase and when the solids mass flow rate and superficial velocity is constant, the pressure gradient increases as the transport pressure is increased. Based on Barth’s pneumatic conveying theory, an empirical correlation of the additional pressure drop coefficient in vertical pipe with Froude number and the solid/gas density ratio was proposed under different pressure. Comparing the pressure drops predicted by the correlation with the experimental data under the pressure of 2.13MPa, it is found that the calculation results are in good agreement with the experimental data.