Experimental investigations on the discharge characteristics of pulverized coal with different external moisture content were carried out in a dense-phase pneumatic conveying facility of top discharge blow tank. The effects of external moisture content on solid discharge rate

solid loading ratio and discharge stability were investigated. The limit and the best values of external moisture content for Neimenggu lignite used in the experiments were obtained. Combined with flowability analysis of the pulverized coal

the discriminate methods of limit and the best external moisture content for discharge process were discussed. The results showed that for pulverized coal with original external moisture content of 3.3%

an obvious electrostatic discharge phenomenon could be observed near the wall of the top discharge blow tank and the riser inlet during the discharge process. When the pulverized coal external moisture content was increased to 10%

arching phenomenon would appear in the top discharge blow tank. The limit external moisture content for Neimenggu lignite was in the range of 8.7%—10%

and its best external moisture content was about 4% corresponding to the maximum solid discharge rate and solid loading ratio

and to the best discharge stability. When the external moisture content was 4%

equal to the best external moisture content obtained by discharge experiments

the flow function reached the maximum value

the cohesion reached the minimum value and the pulverized coal flowability became the best. When the external moisture content was increased from 8.7% to 10%

the pulverized coal flowability turned from the easy flow region to cohesive region and the flowability became worse. When the external moisture content was 10%

the pulverized coal was in the cohesive region which meant difficult to flow. Compared with discharge experiments

the flow function and cohesion obtained by the shear tests could be used as preliminary criterion to judging the limit and best values of external moisture content pulverized coal in industrial applications more conveniently.