In order to meet the flexibility operation needs of coal-fired units under the goal of carbon peak and carbon neutralization, it is imperative for circulating fluidized bed (CFB) units to participate in deep peak regulation. By systematically summarizing deep peak regulation operation practice of existing SC and subcritical-parameter-levels CFB units, the feasibility of deep peak regulation technology of an ultra-supercritical (USC) CFB unit under development and being built is analyzed and demonstrated; meanwhile, the deep peak regulation capacity of the boiler is also predicted. The results show that by analyzing the structural characteristics and design performance of the USC-CFB boiler, for technical problems such as stable combustion under low load, hydrodynamic safety, denitration performance under wide load, and rapid boiler load change rate existing in deep peak regulation, technical measures were implemented by selecting advanced boiler furnace type, adopting good design technology of the secondary rising water wall and uniformity design of bed temperature and bed pressure, strengthening the reducing atmosphere inside the furnace, improving the performance of wear-resistant refractory materials, quickly controlling the furnace bed material stock under variable load, optimizing the control strategy of CFB unit, and so on. The boiler achieved good operation characteristics and good deep peak regulation performance, and the pollutant emissions can steadily achieve ultra-low emission standards. When the USC-CFB unit participates in deep peak regulation, the minimum stable combustion load of the boiler can reach 20~30% BMCR, and a boiler load change rate under 30% BMCR or above could reach 1.5~2% BMCR/min, while that below 30% BMCR could reach 1% BMCR/min. The research results can provide references for the deep peak regulation of in-service supercritical (SC) CFB units and design optimization of similar USC-CFB units.

The effects of NO₂ and NH₃ on Hg⁰ oxidation under fast selective catalytic reduction conditions remain unclear. To address this problem, we performed density functional theory calculations on the V₂O₅/TiO₂(001) surface in four states: clean surface, surface covered by NH₃, surface covered by NO₂, and surface where species are co-adsorbed. On the clean surface, Hg⁰ interacts weakly with oxygen sites; the adsorption energies at terminal (O_t), bridging (O_b) and interfacial bridging (O_b′) oxygen sites are −12.31, −12.58, and −21.22 kcal mol⁻¹, respectively. Direct oxidation by lattice oxygen encounters high activation barriers, ranging from 146.817 to 184.529 kcal mol⁻¹. NH₃ hinders the capture of Hg⁰. Since NH₃ preferentially occupies the vanadium-related active sites, the interaction between Hg⁰ and the catalyst is weakened, and the adsorption energies become less negative, ranging from −11.84 to −11.04 kcal mol⁻¹. NO₂ shows the opposite effect. It strengthens Hg⁰ adsorption near V-centered regions and provides an alternative oxygen source for Hg⁰ oxidation. The NO₂-assisted oxygen-transfer pathways have lower calculated barriers, ranging from 74.581 to 108.545 kcal mol⁻¹. When NH₃ and NO₂ are co-adsorbed, the barrier increases to 113.326 kcal mol⁻¹. Even so, NO₂-derived oxygen provides a relatively lower-energy oxygen-transfer route than lattice oxygen among the pathways examined.