This study aims to examine the effect of an online lime separation system with the semi-dry scrubber and dry lime injection system in a refuse incineration plant. Fine powder was used to prepare different concentrations of lime slurry to remove four combinations of boiler outlet acid gas. Results show that the lime separation can reduce the particle size (D-90) of the hydrated lime from 31 to15 mu m. The removal rate of HCl and SO2 remains over 98% and 90%, respectively. If the SO2 concentration in the gas ismaintained below 200mg/Nm(3) via judicious refuse mixing, the consumption of limewill be most economical. Herein, the payback period of the facility will be approximately three years, and the online lime separation system can enhance the quality of hydrated lime, improve the emissions quality, reduce the consumption of lime, and achieve economic benefits. (c) 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).