直流コロナ放電によるSO_2からの微粒子生成に対する放電極性の影響 Effects of Discharge Polarity on the Fine Particle Formation from SO_2 by DC Corona Discharges
We have measured the effects of discharge polarity on the formation of fine particles from SO<SUB>2</SUB> by DC corona discharges in order to study the role of gaseous ions in the desulfurization process of flue gases by using discharge plasmas. For both positive and negative discharges, the number concentration of the formed particles in SO<SUB>2</SUB>/H<SUB>2</SUB>O/Air mixtures increased with SO<SUB>2</SUB> (0-1 ppm) and H<SUB>2</SUB>O (5 × 10<SUP>2</SUP>-3 × 10<SUP>3</SUP> ppm) concentrations. However, the positive discharges produced a larger amount of particles, and the size of which was larger than those formed by negative discharges. The fraction of charged particles dropped significantly with increasing the number concentration of formed particles in the case of positive discharges, while large fractions of charged particles were observed for negative discharges under all conditions. Mass spectrometric measurements confirmed the formation of H<SUB>2</SUB>SO<SUB>4</SUB> by negative discharges through the detection of HSO<SUB>4</SUB><SUP>-</SUP> ions in the negative ion mass spectra . On the other hand, no positive ions of H<SUB>2</SUB>SO<SUB>4</SUB> were found in the mass spectra of positive ions formed by positive discharges. However, the dominance of H<SUB>3</SUB>O<SUP>+</SUP> ions in the spectra suggested that the formation of OH radicals and the subsequent formation of H<SUB>2</SUB>SO<SUB>4</SUB> took place also in the case of positive discharges. Because of its high electron affinity, H<SUB>2</SUB>SO<SUB>4</SUB> formed by negative discharges is easily ionized to HSO<SUB>4</SUB><SUP>-</SUP> ions by the reactions with the surrounding negative ions, which leads to the charged particle formation via ion-induced nucleation. On the contrary, since H<SUB>2</SUB>SO<SUB>4</SUB> hardly reacts with positive ions and remains neutral with positive ions, the most of particles are formed via homogenous nucleation by positive discharges.
- エアロゾル研究 = Journal of aerosol research
エアロゾル研究 = Journal of aerosol research 23(2), 101-107, 2008-06-20