Using flue-gas waste-heat to dry sludge is an emerging green technology. The sludge drying process is found to be also effective in removal of particulates from the flue-gas. In this paper, we analyze the removal efficiency of such processes measured in both laboratory setting and real power plant environments to determine the important factors that controlling the removal efficiency. The result shows that, for four types of sludge, the removal rates of PM_2.5, PM₁₀, and TSP are in ranges of 18%~42%, 32%~55%, and 39%~62%, respectively. The removal rate of PM_2.5 depends on the microstructure and organic matter content of the sludge. It increases with the sludge packing density and moisture content but decreases with the sludge particulate size. Smaller sludge particulate size is believed to be favoring the formation of abundant water drops in flue-gas which in turn adsorb and combine the micro particles into larger particles.