Low-concentration NOx removal using plasma-chemical hybrid process combined with limestone-gypsum desulfurization
Takeru Itagaki1, Junta Inoue1, Tomoyuki Kuroki1, *, Haruhiko Yamasaki1, Hashira Yamamoto2, Masanori Hattori3, Masaaki Okubo1
* The author to whom correspondence should be addressed.
1 Department of Mechanical Engineering, Osaka Metropolitan University, Japan
2 Nihon Yamamura Glass Co., Ltd., Japan
3 Chubu Electric Power Co., Inc., Japan
Abstract
Nitrogen oxides (NOx) and sulfur oxides (SOx) emitted from thermal power plants are hazardous pollutants causing acid rain and air pollution. To meet the respective emission regulations, NOx is treated using the selective catalytic reduction (SCR) method, while SOx is treated using the lime gypsum method before being discharged via a flue-gas stack. Recently, some local governments and companies have signed environmental protection agreements that impose stricter limits than national emission regulations. Moreover, existing technologies, such as low-NOx burners and SCR, exhibit limitations in achieving further NOx reduction. Therefore, further pollutant reduction measures are required, particularly NOx treatment methods that can be retrofitted into existing flue gas treatment systems in thermal power plants. A plasma-chemical hybrid process (PCHP) offers a promising solution for simultaneous removal of NOx and SOx and can be retrofitted. In this study, laboratory-scale experiments were conducted to evaluate the simultaneous removal of low-concentration NOx and highconcentration SOx using ozone (O3) injection and absorption towers, simulating the integration of PCHP into the absorption tower of flue gas treatment equipment in a coal-fired power plant. The results show that PCHP enables simultaneous removal of low-concentration NOx and high-concentration SO2, although water spray impacts NO oxidation.
Keywords - Low-concentration NOx, plasma-chemical hybrid process, SOx, limestone-gypsum desulfurization.