Development of an Integrated Electrostatic Precipitator and Wet Scrubber System for Controlling Nox and Particulate Matter Emissions From a Semiconductor Manufacturing Process

An integrated electrostatic precipitator (ESP) and wet scrubber system were developed to control nitrogen oxides (NOx) and particulate matter (PM) emissions from a semiconductor manufacturing process. The integrated system consisted of a NO oxidizer, wet scrubber, and ESP. In the NO oxidizer, NO gas was fully oxidized to NO2 by O3 before the flow gas entered the wet scrubber. To control NO2, Na2S was used as a reducing agent, and NaOH was added to suppress H2S in the wet scrubber. The NO2 removal efficiency could be controlled by maintaining an oxidation-reduction potential higher than -330 mV, and H2S was suppressed by keeping the pH higher than 11. To ensure there was no PM peak during the cleaning cycle, dual-type cylindrical collection plates containing a water film were designed. A negative voltage of 15 kV was applied to the collection plate, and the PM removal efficiency was higher than 95%. The experimental particle-removal efficiency was higher than the theoretical value because the ion loading by plasma in the point of use scrubber was greater than the theoretically calculated value. In addition, the PM removal efficiency was maintained at 95% for 60 min through the water film. The integrated ESP and scrubber system were able to control NOx and PM for long periods at a removal efficiency of over 95%.