A wet electrostatic precipitator (WESP) as countermeasure to mist formation in amine based carbon capture

Abstract

This study is to our knowledge the first to evaluate the potential of a wet electrostatic precipitator (WESP) to prevent aerosol formation issues inside amine based carbon capture installations. A WESP is a suitable option since this study proves that it is very efficient for the removal of the mist precursors inside the flue gas to be treated. Although a significant capital investment cost may be involved, energy requirements (i.e. low pressure drop), maintenance and therefore operational costs are expected to be very low. However, it is shown here that the WESP must be installed at the right location, i.e. the flue gas to be treated must contain no or very low levels of SO2. The reason is that the WESP's aerosol removal efficiency decreases strongly in the presence of SO2 gas and in a certain range also with increasing voltages. This limits the positive effect that the WESP has on reducing the MEA emissions from the absorber since a large number of mist formation precursors remain in the flue gas. In the presence of SO2, a WESP can actually produce H2SO4 aerosols. It is shown that these newly created aerosols are very small (low nanometre range). This information is very important for future pilot and demo amine carbon capture installations thinking of implementing a WESP as countermeasure to aerosol formation issues. It implies that no or very low levels of SO2 should still be present in the flue gas before entering the WESP. Since most of the amine carbon capture installations have a pre-scrubber (usually using NaOH to remove residual SO2 in the flue leaving the power plant's FGD) in front of their amine absorber, the WESP must be installed behind this pre-scrubber and not in front of it.