The pressure drop per unit length of pneumatic dense phase transport for pulverized coal with a riser of 20 mm bore stainless steel tube was investigated

and its Zenz-type diagram was obtained.The results revealed that the total pressure drop was mostly attributed to the solids static head and solids friction contribution

and the pressure drop due to gas less than 1% of the total pressure drop might be neglected in this study. Comparing with solids velocity

the solids volume fraction played a leading role for the total pressure gradient.Additionally

the solids friction factor was also investigated

and a correlation was recommended for predicting the solids friction factor

which was consistent with experimental data.