High-temperature corrosion characteristics and mechanisms of heating surfaces under ash deposition conditions in coal/biomass Co-firing utility boilers

Amidst global climate change mitigation, biomass-coal co-firing power generation attracts significant interest due to its environmental benefits and engineering viability, yet the high-temperature corrosion mechanisms under ash deposition remain poorly understood. This study investigated the corrosion of boiler alloy 12Cr1MoV under ash deposits in co-firing systems. A multi-component corrosion platform simulated typical co-firing conditions (20 % corn stalk/lignite energy ratio, 600 °C). Corrosion kinetics, microstructural analysis (SEM-EDS/XRD), and thermodynamic simulations (HSC Chemistry) revealed synergistic corrosion mechanisms. Key findings: (1) Corn stalk ash promoted corrosion more severely than coal ash; mixed ash accelerated protective scale failure via low-melting eutectics, increasing corrosion rates by 1.7 × versus single ash. (2) Corrosion rates under HCl (500 ppm) significantly exceeded those under SO₂ (500 ppm), confirming Cl⁻-induced Cr₂O₃ breakdown dominates corrosion. (3) Coupled mixed ash and acidic gases (HCl/SO₂) yielded an extreme corrosion rate of 42.60 mm/a – a 3-4 × increase over single-factor conditions – attributed to synergistic Cl⁻ enrichment in ash pores and sulfide diffusion. This work systematically elucidates the complex effects of ash composition (biomass ash, coal ash, mixed ash), gaseous components (HCl, SO₂), and their synergy on 12Cr1MoV corrosion in co-firing systems, quantifying peak corrosion rates from ash-gas interactions. It provides a theoretical basis for corrosion-resistant material design and mitigation in biomass-co-firing power plants.