White smoke emission from a semiconductor manufacturing plant

Semiconductor manufacturing involves processes which emit various gaseous and particulate pollutants. One of the common problems in the industry is the emission of white smoke from stacks of wet scrubbers. This study analyzed the physical and chemical characteristics of the white smoke in one of the semiconductor plants in Taiwan. It was observed that the medium diameter of the emitted particles is about 0.1 μm, which will grow further into 0.1-1.0 μm size range due to the condensation of water vapor onto these particles under certain meteorological conditions. These 0.11.0 μm particles are responsible for the white smoke since they have a high light scattering efficiency. In the waste stream from the wet scrubber, the main chemical species were found to be silica, monomeric silica, ammonium, and chloride for particulate pollutants, and ammonium and chloride for gaseous pollutants. A wet Electrostatic Precipitator (ESP) installed behind the wet scrubber was shown to be able to eliminate white smoke emission due to efficient removal of submicrometer particles.