Based on a self-developed dense phase pneumatic conveying system

conveying tests of three lignite pulverized coal with different mean particle sizes using N2 as carrier gas were carried out. The Hurst exponents of pressure drop fluctuation signals in horizontal pipe and mass pulsations of material storage tank were calculated using rescaled range analysis. The standard deviations of mass pulsations were analyzed. The Hurst exponent and standard deviation were used as an indicator of conveying stability. The flow stability of conveying pipe was well characterized by Hurst exponents of pressure drop fluctuation signals (Hdp)

while the discharge stability of material tank was not well characterized by Hurst exponents of mass pulsations (Hma) and standard deviation analysis was required. Conveying stability was investigated according to the ratio of superficial gas velocity to saltation velocity (K). At the left side of K=1.5

Hdp decreased with the decrease of K

the flow regime in gas-solids horizontal conveying pipe was changed and even caused a pipe blockage

the flow stability of conveying pipe became worse. Meanwhile

the standard deviation of mass pulsations increased as K decreased

the discharge stability of material tank deteriorated

and conveying stability became worse. At the right side of K=1.5

as K increased

decreasing trend of Hdp was not obvious

through combined analysis with standard deviation analysis

discharge stability became worse and might cause interruption of discharging.