The special process for producing carbon black precludes the application of traditional, mature flue-gas treatments (e.g., SNCR and SCR) to reduce NOx emissions. However, simultaneous removal of sulfur and nitrogen by the combination of ozone oxidation with limestone gypsum wet scrubbing is suitable for the conditions found in carbon black flue gas. This article presents the first industrial-scale deployment of this technology in a 100000 t/year carbon black production line (flue-gas volume of 60000 Nm(3)/h). Optimizations were performed by studying the effectiveness of desulfurization and denitration for various operating parameters such as O-3/NOx molar ratio, spray-tower liquid/gas ratio, initial NOx concentration, and forced oxidation. The results showed that (1) the O-3/NOx molar ratio is the determining factor in denitration efficiency, (2) both forced oxidation and increasing initial NO concentration improve the denitration efficiency but reduce the desulfurization efficiency, and (3) increasing the liquid/gas ratio can improve the desulfurization efficiency but has little effect on denitration. The maximum desulfurization and denitration efficiencies of the system can be up to 98% and 95%, respectively, with SO2 and NOx levels of 1000 mg/Nm(3) (6% O-2) and 900 mg/Nm(3) (6% O-2) dropping to 20 mg/Nm(3) (6% 02) and 45 mg/Nm(3) (6% O-2), respectively.