Electrostatic charging of fine hydrated Lime with an average primary particle size of 2.5 mu m under various transport conditions is studied. The charging tendency is evaluated in terms of charge-to-mass ratio, which is defined as the ratio of the accumulated charges to the powder weight, The charge-to-mass ratio of the hydrated lime is investigated at various gas velocities and powder mass flow rates. The effects of transport tube materials and surfactants are studied. In addition, the bipolar charging phenomenon that is commonly observed during silo filling is examined. The parameter of the powder mass flow rate is not generally considered in the theoretical formulation of charge transfer; however, this study shows that the powder mass flow rate has significant effects on the charge accumulation on powder. An empirical correlation of charge-to-mass ratio as a function of the gas velocity and powder mass flow rate is presented. The bipolar charging appears to occur during powder transport. Surfactant-modified hydrates exhibit charging behavior significantly different from that of toners with charge-control agents. While high solids loading favors low charge accumulation, it also increases the chances of discharging.