Comprehensive evaluation of flue gas desulfurization and denitrification technologies of six typical enterprises in Chengdu, China

Post-combustion flue gas desulfurization and denitrification technologies are essential in achieving the full compliance of fine particulate matter (PM₂.₅, aerodynamic diameter less than 2.5 μm) air quality standards by 2030 in China as sulfur dioxide (SO₂) and nitrogen oxides (NOX) are the main precursors of PM₂.₅. Some studies have addressed the performance evaluation of desulfurization technology, but none included the water-soluble ions (sulfate (SO₄²⁻), nitrate (NO₃⁻), etc.) as an indicator nor accounted for uncertainty involved. In this study, we present a multilevel fuzzy method that integrates the analytic hierarchy process with fuzzy theory, defines SO₄²⁻concentration as a new environmental indicator, and is supplemented with an uncertainly analysis and apply the method for the techno-economic and environmental evaluation of desulfurization and denitrification technologies in six typical enterprises (including two power plants and three industrial production plants and a waste incineration plant) in Chengdu, China. The evaluation shows that first, the fluctuating desulfurization rate and the dosage leads to changed ranking of the economic and technical secondary evaluation results, with the overall comprehensive evaluation ranks unchanged. Second, from the perspective of environmental protection agency and the public, if the environmental indicators are empowered, the lower the SO₄²⁻concentration of an enterprise, the better its evaluation ranking will be and vice versa. Third, if we re-empower from the perspective of the enterprise, under the condition that the technical feasibility is met and the environmental indicators are basically up to standard, the low-cost removing process is more likely to be the tendency of the enterprise. In summary, the findings of the study have led to the conclusions that (1) for the power industry, the integration of desulfurization, denitrification, and dedusting technologies should be promoted rigorously; (2) the non-power industry should continue the end-of-pipe treatment and environmental protection regulatory policies of the power industry; and (3) the energy industry structure should be optimized with enhanced end-of-pipe control technologies to achieve deep reduction of air pollutants.