Full-scale evaluation of SO2 capture increase for semi-dry FGD technology

Abstract

This paper reports on a full-scale investigation of a possible increase of the SO2 capture ratio in current semi-dry flue gas desulphurization (FGD) technology. The FGD unit is used for two 130 t/h steam PC boilers burning a blend of lignite and hard coal with dry ash-free sulphur content at 1.83%. The FGD unit has been designed to reach an SO2 emission limit of 1350 mg/Nm(3). The aim of the experimental work presented in this paper was to investigate the possibility of reaching SO2 emission targets of 500 and 200 mg/Nm(3). The investigation sought to determine the real correlation of SO2 capture ratio with Ca/S and with the difference of dry-bulb temperature and dew point in the absorber AtAD. Generally, the SO2 capture correlation with Ca/S has flat characteristics at a capture ratio >90%, which is required to reach the 200 mg/Nm(3) target. In this case, lowering the AtAD in the absorber has only a weak effect. The 500 mg/Nm(3) target requires an SO2 capture ratio of about 80%; in this case lowering the AtAD by about 7 degrees C increases the SO2 capture by 10% points at the same Ca/S ratio. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.