Operational evaluation demonstrates enhanced mercury removal in a 660 MW coal power unit, indicating that coordinated SCR-WFGD optimization eliminates the need for dedicated hardware.
Coal-fired power plants equipped with selective catalytic reduction (SCR) and wet flue-gas desulfurization (WFGD) can co-control mercury, but performance is limited by incomplete upstream Hg0 oxidation and downstream re-emission. This study evaluated a 660 MW unit using gas-, liquid-, and solid-phase measurements and coordinated single-factor and coupled operating tests. Under baseline conditions, SCR Hg0 oxidation was 31.66%, WFGD Hg2+ capture was 73.79%, and net mercury removal was 31.08%, with a stack HgT concentration of 4.70 µg/Nm3. Coupled optimization increased SCR Hg0 oxidation to 69.76% and WFGD Hg2+ capture to 96.05%, reduced the re-emission index from 0.596 to 0.250, and raised net removal to 70.83%. SCR inlet temperature, equivalent space velocity, and catalyst health were the dominant upstream factors, while S(IV), oxidation–reduction potential (ORP), slurry pH, and oxidation air supply governed downstream stabilization. A practical operating window was identified near 340 °C, with a normalized stoichiometric ratio (NSR) of approximately 1.0, high ammonia injection uniformity, pH of 5.5–6.0, ORP of approximately 200 mV, and S(IV) of approximately 2 mmol/L. The results show that coordinated operation of existing SCR–WFGD equipment can substantially reduce stack mercury without dedicated mercury-control hardware, provided that NH3 slip, SO3-related risk, catalyst condition, and absorber stability are simultaneously constrained.
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Liu et al. (2026) studied this question.
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